CSarp

 

Versions:


C# 1.0:

Released in January 2002, C# 1.0 marked a major milestone in the evolution of programming languages, offering developers a solid foundation for building robust applications.

The core of C# 1.0 revolves around basic object-oriented programming (OOP), enabling the use of classes and interfaces to structure code. It also introduced enums to manage named constants, structs for lightweight data types, and delegates to handle method references securely. Events became an essential feature for building event-driven applications, especially in GUI development.

Error handling was made simpler with try, catch, and finally blocks, allowing developers to manage exceptions gracefully and ensure code stability.

These features provided a comprehensive toolkit, making C# a versatile language for developers looking to build maintainable, efficient, and scalable software.

C# 1.0 (Released: January 2002)

  • Basic OOP support
  • Enums, structs, delegates, and events
  • Try, catch, finally for exception handling
  • Namespaces


C# 2.0:

C# 2.0 (Released: November 2005) brought significant improvements to the language, making it even more powerful and flexible for developers.

Key features introduced include Generics, which enabled the creation of type-safe collections and other data structures, reducing the risk of runtime errors. The introduction of Anonymous Methods allowed developers to define inline delegates without needing a separate named method, streamlining code in some scenarios.

C# 2.0 also introduced Nullable Types, allowing value types (like int) to be assigned a null value, which was previously impossible. The yield keyword brought Iterators, making it easier to implement custom enumerators, improving the handling of sequences.

Another notable feature was Partial Classes, which allowed large class definitions to be split across multiple files, improving code organization. Lastly, Constraints on Generics were added, enabling developers to specify restrictions on the types that can be used with generics, providing more control over generic methods and classes.

These features made C# 2.0 a more expressive and developer-friendly language, allowing for cleaner, more efficient, and more maintainable code.

C# 2.0 (Released: November 2005)

  • Generics
  • Anonymous methods
  • Nullable types
  • Iterators (yield keyword)
  • Partial classes
  • Constraints on generics

C# 3.0: 

C# 3.0 (Released: November 2007) introduced a number of groundbreaking features that made the language even more concise and powerful, especially for working with data.

One of the standout features was Language Integrated Query (LINQ), which provided a unified, integrated syntax for querying collections, databases, and other data sources directly within the language. This made it much easier to work with data and reduced the need for external query languages like SQL.

Anonymous Types allowed developers to create objects on the fly without having to define a separate class, simplifying code in scenarios where only temporary, ad-hoc objects were needed. Lambda Expressions brought a way to write concise, inline function definitions, which were especially useful for LINQ queries and other functional programming patterns.

C# 3.0 also introduced Extension Methods, allowing developers to add methods to existing types without modifying the original code. This provided a powerful way to enhance libraries or frameworks without changing their implementation.

Object Initializers simplified object creation by allowing developers to initialize objects directly in the constructor using a shorthand syntax, making code more readable and efficient.

Lastly, Automatic Properties allowed properties to be declared without the need to manually define backing fields, reducing boilerplate code and improving maintainability.

These features made C# 3.0 a more modern, concise, and expressive language, especially when working with data and simplifying common coding tasks. 

C# 3.0 (Released: November 2007)

  • Language Integrated Query (LINQ)
  • Anonymous types
  • Lambda expressions
  • Extension methods
  • Object initializers
  • Automatic properties


C# 4.0

C# 4.0 (Released: April 2010) brought several features that enhanced flexibility and interoperability, particularly in dynamic and COM-related scenarios.

One of the key additions was the Dynamic Language Runtime (DLR), which introduced the dynamic keyword. This allowed for runtime type resolution, enabling more flexible coding practices when interacting with dynamic languages or working with types that are not known until runtime.

The version also introduced Named and Optional Arguments, making method calls more flexible. Developers could now provide parameters in any order and assign default values to arguments, simplifying method calls and improving code readability.

COM Interoperability Enhancements made it easier to integrate with COM objects, allowing smoother interaction with legacy systems. Additionally, Covariant Return Types allowed methods to be overridden with more derived return types, increasing the expressiveness of polymorphism in object-oriented designs.

C# 4.0 also included Improved COM Interop, which enhanced support for calling COM objects and handling their parameters more efficiently.

These additions made C# 4.0 a more versatile language, particularly for applications that needed dynamic behavior or involved integration with older COM-based systems.

C# 4.0 (Released: April 2010)

  • Dynamic Language Runtime (DLR)
  • Named and optional arguments
  • COM interoperability enhancements
  • Covariant return types
  • Improved COM interop


C# 5.0 (Released: August 2012)

C# 5.0 (Released: August 2012) focused on simplifying asynchronous programming and improving diagnostics, making it easier for developers to write and debug code.

One of the most significant additions was Asynchronous Programming (async/await). The introduction of the async and await keywords greatly simplified writing asynchronous code, making it easier to work with tasks and avoid callback hell. This feature improved the readability and maintainability of applications that required asynchronous operations, especially in UI and I/O-bound applications.

Caller Information Attributes provided a way to automatically capture information about the calling method, line number, and file path. This made logging, debugging, and error reporting more informative and efficient, as developers could easily trace where issues occurred without manually passing this information.

C# 5.0 also brought Improved Compiler Diagnostics, offering better support for warnings and errors, which helped developers identify issues earlier in the development process and improved overall code quality.

These features made C# 5.0 a more powerful and developer-friendly language, particularly in the realm of asynchronous programming and debugging.

C# 5.0 (Released: August 2012)

  • Async/await for asynchronous programming
  • Caller information attributes
  • Improved compiler diagnostics


C# 6.0 (Released: July 2015)

C# 6.0 (Released: July 2015) brought a series of syntactic enhancements that made the language more concise, readable, and easier to work with.

One of the standout features was Expression-Bodied Members, which allowed method, property, indexer, and operator definitions using a more concise syntax. This helped reduce boilerplate code, making it cleaner and more readable.

Interpolated Strings introduced the $ syntax, making string formatting simpler and more intuitive. Developers could now embed expressions directly within strings, making code more readable and reducing the need for String.Format or concatenation.

The Null-conditional Operators (?.) simplified null checks, allowing for safer access to members of potentially null objects. This helped avoid NullReferenceException errors by allowing short-circuit evaluation when an object is null.

Exception Filters enabled developers to specify conditions for catching exceptions, providing more fine-grained control over exception handling. This feature made it easier to handle specific error cases without catching all exceptions indiscriminately.

Lastly, Readonly Auto-Properties allowed developers to define properties that could only be set in constructors, simplifying the creation of immutable objects.

These features made C# 6.0 a more expressive and streamlined language, enhancing productivity and reducing the complexity of everyday tasks like string formatting, null checking, and exception handling.

C# 6.0 (Released: July 2015)

  • Expression-bodied members
  • Interpolated strings
  • Null-conditional operators (?.)
  • Exception filters
  • Readonly auto-properties


C# 7.0 (Released: March 2017)

C# 7.0 (Released: March 2017) introduced a set of features that enhanced code clarity, performance, and flexibility, making it easier for developers to write efficient and maintainable code.

Out Variables allowed out parameters to be declared inline, simplifying code and making it more concise when working with methods that use out parameters.

The introduction of Tuples provided a lightweight way to return multiple values from a method without the need for creating custom classes or structs. This feature made it easier to group data together and improve method signatures.

Ref Locals and Returns allowed methods to return references to variables instead of copying values, which improved performance, especially when working with large data structures.

Pattern Matching enhanced the is expression, allowing for more sophisticated type checks and conditions. This made it easier to work with complex data types and perform pattern-based matching in a cleaner way.

With Local Functions, developers could now define methods inside other methods, improving code organization and scope management. This allowed for more modular, self-contained logic in complex methods.

Finally, Readonly Structs allowed developers to create immutable structs, which could lead to better performance and safety when working with value types.

C# 7.0’s features streamlined code, improved performance, and made the language more expressive, giving developers new tools for writing cleaner, more efficient applications.

C# 7.0 (Released: March 2017)

  • Out variables
  • Tuples
  • Ref locals and returns
  • Pattern matching
  • Local functions
  • Readonly structs


C# 8.0 (Released: September 2019)

C# 8.0 (Released: September 2019) introduced several powerful features that focused on improving safety, performance, and the syntax of the language.

The standout feature was Nullable Reference Types, which helped prevent null reference exceptions by allowing developers to explicitly declare whether a reference type can be null. This improved code safety and helped avoid many common runtime errors.

Async Streams allowed for asynchronous iteration using IAsyncEnumerable, enabling developers to work with data streams in an asynchronous manner, making it easier to process large or streaming datasets without blocking the main thread.

Switch Expressions provided a more concise, expression-based form of the traditional switch statement. This made code more readable and expressive, allowing for inline pattern matching and simplified switch logic.

Indices and Ranges introduced the ^ operator to index from the end of a collection and the concept of ranges for slicing collections. This feature made working with arrays and collections more intuitive and flexible.

Finally, Null-Coalescing Assignment (??=) provided a shorthand for assigning a value to a variable only if it is null, making null checks and assignments more concise.

C# 8.0’s features enhanced developer productivity by making the language safer, more efficient, and easier to work with, especially in scenarios involving asynchronous programming, null handling, and collection manipulation.

C# 8.0 (Released: September 2019)

  • Nullable reference types
  • Async streams
  • Switch expressions
  • Indices and ranges
  • Null-coalescing assignment


C# 9.0 (Released: November 2020)

C# 9.0 (Released: November 2020) introduced features aimed at simplifying immutable data handling, improving object manipulation, and enhancing pattern matching capabilities.

One of the major highlights was the introduction of Record Types. The new record keyword allowed developers to create immutable types with value-based equality, making it easier to work with data that should not change once initialized, such as data transfer objects (DTOs).

Init-only Properties provided a way to set properties during object initialization but prevent them from being modified afterward. This improved the creation of immutable objects, offering flexibility during initialization while ensuring their state remained unchanged after construction.

With-expressions allowed the creation of a new object by copying values from an existing one, with some properties changed. This made it easier to work with immutable objects, enabling simple object modifications without having to manually copy fields or properties.

Pattern Matching Enhancements expanded the capabilities of pattern matching, allowing for more complex conditions and matching scenarios, such as matching on types and extracting values directly within the patterns. This made working with data more expressive and less verbose.

C# 9.0’s features streamlined the handling of immutable data, improved the flexibility of object creation and modification, and enhanced pattern matching, making it an even more powerful and developer-friendly language.

C# 9.0 (Released: November 2020)

  • Record types
  • Init-only properties
  • With-expressions
  • Pattern matching enhancements


C# 10.0 (Released: August 2022)

C# 10.0 (Released: August 2022) brought several enhancements that simplified code structure, improved developer productivity, and expanded the language’s capabilities for working with immutable types.

One of the key features was Global Using Directives, which allowed using directives to be declared globally across a project, reducing redundancy and making code cleaner, especially in large projects. This eliminated the need to repeatedly include the same using directives in every file.

File-Scoped Namespace simplified namespace declarations by allowing them to be written on a single line instead of wrapping the entire file in a namespace block. This made the code more compact and improved readability, particularly for smaller files.

Constant Interpolated Strings enabled the use of interpolated strings in const declarations, offering more flexibility in defining constant values that include dynamic expressions, such as variables, directly within the string.

C# 10.0 also improved Lambda Expressions, adding support for natural types for lambdas, which allowed for more intuitive type inference and cleaner syntax when working with lambda expressions.

Finally, Record Structs were introduced, allowing developers to create immutable structs with the benefits of record types, such as value-based equality and immutability, but with the performance advantages of value types.

These features made C# 10.0 a more concise, powerful, and flexible language, improving how developers manage namespaces, constants, and immutable data.

C# 10.0 (Released: August 2022)

  • Global using directives
  • File-scoped namespace
  • Constant interpolated strings
  • Improvements to lambda expressions
  • Record structs


C# 11.0 (Released: November 2022)

C# 11.0 (Released: November 2022) introduced several features that focused on improving code safety, flexibility, and pattern matching, making it easier to work with data and handle strings in more versatile ways.

One of the standout features was Required Members, which allowed developers to enforce that certain properties must be initialized when an object is created. This feature helped ensure that objects are always in a valid state, preventing errors related to uninitialized properties.

Raw String Literals were introduced to simplify the handling of multi-line strings and allow for more flexible string formatting. This feature made it easier to work with strings that contain special characters, line breaks, or require minimal escaping.

List Patterns enhanced pattern matching, enabling developers to match entire collections (like arrays or lists) directly in switch statements or other pattern-matching expressions. This simplified working with collections and made code more expressive when checking for specific patterns within them.

Finally, UTF-8 String Literals allowed developers to define string literals using UTF-8 encoding, providing better performance and memory efficiency when dealing with text data, especially in scenarios involving large or internationalized datasets.

C# 11.0's features made the language more expressive, flexible, and efficient, particularly in the areas of data handling, pattern matching, and string manipulation.

C# 11.0 (Released: November 2022)

  • Required members
  • Raw string literals
  • List patterns
  • UTF-8 string literals


C# 12.0 (Expected: 2024/2025)

C# 12.0 (Expected: 2024/2025) is set to introduce several exciting features aimed at simplifying syntax, improving performance, and enhancing the language's flexibility for developers.

Primary Constructors will streamline the way classes and structs are constructed, allowing for a more concise syntax by defining parameters directly within the class or struct declaration. This will reduce boilerplate code and make object construction more intuitive.

Lambda Expression Improvements will enhance lambda type inference and typing, making lambdas even more expressive and easier to work with. These improvements are expected to simplify lambda usage, especially in complex scenarios, while improving type safety and code readability.

In addition, Improved Performance will be a key focus, with new features designed to further reduce the overhead of runtime operations, making C# applications even more efficient. These improvements will help developers build faster and more scalable applications without sacrificing readability or maintainability.

C# 12.0's planned features aim to make the language more concise, efficient, and developer-friendly, continuing to build on the innovations of previous versions while pushing C# into new levels of performance and ease of use.


C# 12.0 (Expected: 2024/2025)

  • Primary constructors
  • Lambda expression improvements
  • Improved performance



C# Deprecations:

  • var with arrays of a known type: Implicit typing with arrays was discouraged in favor of more explicit types for better clarity.
  • dynamic in certain scenarios: Dynamic typing is discouraged unless necessary. Statically typed solutions are preferred for better performance and safety.
  • Tuple in favor of ValueTuple: The older System.Tuple class was replaced with ValueTuple, providing better performance and flexibility, especially with named elements and value semantics.
  • ISerializable: The ISerializable interface is being phased out in favor of modern serialization methods like System.Text.Json and Newtonsoft.Json, which offer better performance and features.
  • Old ASP.NET WebForms: C# has moved away from ASP.NET WebForms, focusing on modern web development frameworks like ASP.NET Core, which are more modular, flexible, and performant.

These deprecations reflect a shift towards more modern, efficient, and maintainable coding practices and frameworks in C#.



C# Deprecations and Alternatives:

var with arrays of a known type

Deprecation: Implicit typing with arrays was discouraged.

Alternative: Use explicit types for arrays to ensure clarity and avoid ambiguity.

Example:

int[] numbers = new int[] { 1, 2, 3 };  // Instead of var


dynamic in certain scenarios

Deprecation: The use of dynamic typing is discouraged unless necessary.

Alternative: Use statically-typed solutions wherever possible for better performance, type safety, and debugging.

Example:

var value = 10;  // Instead of dynamic variable if type is known


Tuple in favor of ValueTuple

Deprecation: The older System.Tuple class is replaced with ValueTuple for better performance.

Alternative: Use ValueTuple for value types and named tuple elements.

Example:

// Instead of System.Tuple

(int, string) tuple = (1, "hello"); // Use ValueTuple


ISerializable

Deprecation: ISerializable interface is being phased out in favor of more modern serialization methods.

Alternative: Use System.Text.Json or Newtonsoft.Json for serialization and deserialization.

Example with System.Text.Json:

using System.Text.Json;

var json = JsonSerializer.Serialize(myObject);  // Instead of using ISerializable


Old ASP.NET WebForms

Deprecation: ASP.NET WebForms is being replaced with more modern frameworks like ASP.NET Core.

Alternative: Use ASP.NET Core or Blazor for modern web development.

Example with ASP.NET Core:

// Instead of WebForms

public class HomeController : Controller

{

    public IActionResult Index()

    {

        return View();

    }

}


These alternatives align with modern C# development practices and offer improved performance, scalability, and maintainability.



Events IN CSHARP:

A delegate represents a method signature for event handlers.

An event is declared using the event keyword followed by a delegate type.

Methods are added to an event using the += operator.

Methods are removed from an event using the -= operator.

Triggering the event notifies all subscribed handlers.

An event handler is a method that matches the delegate signature and responds to the event.

The publisher is the class that declares and raises the event.

The subscriber is the class or method that listens for and responds to the event.

Events encapsulate the delegate, hiding the delegate's Invoke method from external access.

Custom EventArgs classes can be used to pass additional data with the event.

A protected virtual method (e.g., OnMyEvent) is used to raise the event and allow derived classes to override event-raising behavior.



Enums IN CSHARP:

  • An enum is a distinct value type that defines a set of named constants.
  • An enum is declared using the enum keyword, followed by the enum name and the list of constant values.
  • By default, enum values are assigned integer values, starting at 0, and increment by 1, but custom values can be assigned explicitly.
  • The enum type is used to represent a variable that can hold one of the defined constant values.
  • Enum constants are typically represented as integers, but the underlying type can be specified (e.g., byte, short).
  • The enum value is implicitly cast to its underlying integer value when used in expressions.
  • Enums are commonly used to define sets of related options, like days of the week or error codes.
  • An enum can be used in a switch statement for easier decision making based on the enum values.
  • The enum values are distinct, which means you can't assign any value other than those defined in the enum.
  • Flags enums allow combining multiple values using bitwise operations (e.g., | for OR).
  • Enum values can be accessed using Enum.GetValues() or Enum.GetName() for dynamic operations.
  • Enum comparisons are based on the underlying integer values, but enums are type-safe and prevent invalid values.
  • Enums can be cast to and from their underlying type (e.g., integer), but it is typically done explicitly to maintain clarity.
  • Enum to string conversion is possible using ToString() or Enum.GetName() methods.
  • Custom enum values can be used to enhance code readability and prevent magic numbers.


Abstraction:

Abstraction in C# is a fundamental concept in object-oriented programming (OOP) that allows you to hide complex implementation details and show only the essential features of an object. 

Abstraction helps to create a clear separation between what an object does and how it does it, improving code readability and maintainability..

In C#, abstraction can be achieved by using Abstract Classes, Abstract Methods, Interfaces, Encapsulation.

Abstract Classes: Provide a base class with both abstract methods (without implementation) and concrete methods (with implementation).

Abstract Methods: Must be implemented by any non-abstract derived class.

Interfaces: Define a contract that implementing classes must follow, without providing any implementation.

Encapsulation: Hides internal state and requires interaction through public methods or properties.



1. Example using Abstract Classes:


Coding:

using System;


public abstract class Vehicle

{

    public abstract void Start(); // Abstract method (no implementation)

    

    public void Refuel() // Concrete method (with implementation)

    {

        Console.WriteLine("The vehicle is being refueled.");

    }

}


public class Car : Vehicle

{

    public override void Start()

    {

        Console.WriteLine("Car is starting.");

    }

}



Explanation:

In this example, `Vehicle` is an abstract class with an abstract method `Start` (which must be implemented by derived classes) and a concrete method `Refuel` (with its own implementation). The `Car` class inherits from `Vehicle` and provides its specific implementation for the `Start` method.




2. Example using Abstract Methods

public abstract class Document

{

    public abstract void Print();

}


public class PDFDocument : Document

{    

    public override void Print()

    {

        Console.WriteLine("Printing PDF document.");

    }

}


Explanation:

Here, Print is an abstract method in the Document class.

The PDFDocument class inherits from Document and provides a concrete implementation of the Print method, which outputs "Printing PDF document." to the console. 

This setup enforces a common method contract for all document types while allowing each type to define its specific printing behavior.




3. Example using Interfaces

public interface IDrawable

{

    void Draw(); // Method declaration

}


public class Rectangle : IDrawable

{

    public void Draw()

    {

        Console.WriteLine("Drawing a rectangle.");

    }

}


In this example, `IDrawable` is an interface with a `Draw` method that must be implemented by any class 

that uses the interface. 

The `Rectangle` class implements `IDrawable` and provides its own implementation of the `Draw` method, which outputs "Drawing a rectangle."





4.  Example using Encapsulation


public class Person

{

    private string name; // Private field


    public string Name // Public property

    {

        get { return name; }

        set { name = value; }

    }

    

    public void DisplayName()

    {

        Console.WriteLine("Name: " + name);

    }

}


In this example, the `name` field is private and not accessible directly from outside the `Person` class. Instead, access is provided through the public `Name` property, which allows both getting and setting the value. The `DisplayName` method prints the value of `name` to the console.





Encapsulation in C#:
Encapsulation ensures that data and methods are bundled together, protected, and exposed in a controlled manner. This approach hides complexity and maintains a consistent interface by using classes to provide a single unit of functionality. Properties provide a controlled way to access data with optional validation or logic, whereas fields are typically private and directly hold the data. Encapsulation supports abstraction by hiding implementation details and exposing only necessary functionality through a clear interface. Access control restricts direct access to data, ensuring integrity through private fields and controlled exposure via methods or properties. It shields the internal state from unauthorized modifications by using validation logic in properties and methods. Access modifiers (public, private, protected, internal) control how data and methods are exposed, including to derived classes. Properties can be defined as read-only (only get access) or write-only (only set access), allowing control over how data is accessed and modified. Collections can be encapsulated by exposing them as read-only interfaces to prevent external modification while still allowing internal manipulation.

Encapsulation also supports the Dependency Inversion Principle by allowing high-level modules to interact with abstractions rather than concrete implementations, which promotes flexibility and reduces coupling. It facilitates defensive programming by providing controlled access to the internal state of an object, including validation checks to prevent invalid state changes. Encapsulation is used in various design patterns such as Singleton, Factory, and Proxy for controlled object creation and access. It helps manage access to shared resources and reduces issues related to concurrent access. Encapsulation works alongside principles like Interface Segregation to ensure that interfaces are designed to provide only the methods relevant to the implementing class. Proper encapsulation facilitates unit testing by allowing you to test the class’s public interface while keeping internal details hidden. It also ensures data integrity by providing mechanisms to prevent unauthorized or inconsistent modifications to an object's state. Although encapsulation is crucial, reflection can be used to bypass it, allowing access to private members and potentially leading to maintenance challenges. Additionally, the `internal` access modifier allows access within the same assembly, providing a way to encapsulate functionality shared within a specific scope but hidden from external consumers.



Example Encapsulation:
using System;

namespace EncapsulationExample
{
    // BankAccount class demonstrates encapsulation
    public class BankAccount
    {
        // Private fields to hold account data
        private string _accountNumber;
        private decimal _balance;

        // Constructor to initialize a new account
        public BankAccount(string accountNumber, decimal initialBalance)
        {
            _accountNumber = accountNumber;
            _balance = initialBalance;
        }

        // Public property to get the account number (read-only)
        public string AccountNumber
        {
            get { return _accountNumber; }
        }

        // Public property to get the balance (read-only)
        public decimal Balance
        {
            get { return _balance; }
        }

        // Public method to deposit money
        public void Deposit(decimal amount)
        {
            if (amount <= 0)
            {
                throw new ArgumentException("Deposit amount must be positive.");
            }
            _balance += amount;
        }

        // Public method to withdraw money
        public bool Withdraw(decimal amount)
        {
            if (amount <= 0)
            {
                throw new ArgumentException("Withdrawal amount must be positive.");
            }
            if (amount > _balance)
            {
                return false; // Insufficient funds
            }
            _balance -= amount;
            return true;
        }

        // Private method to perform internal validation (complex logic hidden from users)
        private bool ValidateTransaction(decimal amount)
        {
            // Example validation logic
            return amount > 0 && amount <= _balance;
        }
    }

    class Program
    {
        static void Main()
        {
            // Create a new BankAccount instance
            BankAccount account = new BankAccount("123456789", 1000m);

            // Display initial balance
            Console.WriteLine($"Account Number: {account.AccountNumber}");
            Console.WriteLine($"Initial Balance: {account.Balance}");

            // Deposit money
            account.Deposit(500m);
            Console.WriteLine($"Balance after deposit: {account.Balance}");

            // Withdraw money
            bool success = account.Withdraw(200m);
            Console.WriteLine($"Withdrawal successful: {success}");
            Console.WriteLine($"Balance after withdrawal: {account.Balance}");

            // Try to withdraw more money than available
            success = account.Withdraw(2000m);
            Console.WriteLine($"Withdrawal successful: {success}");
            Console.WriteLine($"Balance after withdrawal attempt: {account.Balance}");
        }
    }
}


Explanation:
Private Fields: The _accountNumber and _balance fields are private, which means they are only accessible within the BankAccount class. This hides the internal state from outside classes.

Public Properties: AccountNumber and Balance are public properties that provide controlled access to the private fields. AccountNumber is read-only, and Balance is read-only as well.

Public Methods: Deposit and Withdraw methods provide controlled ways to modify the balance. They include validation logic to ensure that the operations are valid (e.g., no negative deposits).

Private Method: The ValidateTransaction method is private and used internally to validate transactions. This hides the complexity of the validation logic from users of the class.

By encapsulating the data and methods in the BankAccount class, we hide the internal complexity and provide a clear, controlled interface for interacting with bank accounts.






Finalize:
*********
In C#, the Finalize method (often seen as a destructor) is used to clean up unmanaged resources in classes that handle such resources. However, it can introduce overhead due to delayed garbage collection and additional processing since objects with finalizers are queued for finalization.

Key Points:
Purpose: Finalizers clean up unmanaged resources when an object is collected by the garbage collector.

Overhead: Finalizers lead to delayed resource release and increased memory usage because objects aren't collected immediately.

Best Practice: Implement the IDisposable interface for explicit resource management. This allows users to release resources promptly and avoid relying solely on finalizers.

Suppress Finalization: After implementing Dispose, call GC.SuppressFinalize(this) to prevent the finalizer from executing, reducing overhead.


Dispose:
********
Purpose: The Dispose method, part of the IDisposable interface, allows for the deterministic release of managed and unmanaged resources when they are no longer needed.

Deterministic Cleanup: By implementing Dispose, developers can control exactly when resources (like file handles and database connections) are freed, avoiding reliance on the garbage collector.

Implementation Steps:

Implement IDisposable: Create a class that includes the IDisposable interface.
Define the Dispose Method: This public method is called to release resources.
Suppress Finalization: Call GC.SuppressFinalize(this) in Dispose to prevent the finalizer from executing if resources are already cleaned up.
Protected Dispose Method: Optionally create a protected method to handle both managed and unmanaged resource cleanup differently.
Usage: It's best practice to use a using statement when working with objects that implement IDisposable, ensuring resources are automatically released.

Key Benefits
Prevents Resource Leaks: Ensures timely cleanup of resources, which is essential for performance and reliability.
Improves Code Clarity: Provides a clear pattern for managing resources, making code easier to maintain.
Overall, implementing the Dispose pattern is crucial for effective resource management in .NET applications.





Partial Class IN CSHARP:

  • A partial class allows the definition of a class to be split across multiple files.
  • Partial classes are declared using the partial keyword before the class keyword.
  • Each part of the partial class must be marked with the partial keyword.
  • All parts of a partial class must be in the same namespace and have the same access modifier.
  • Partial classes are typically used to organize large classes or to separate auto-generated code from custom code (e.g., designer files in UI frameworks).
  • When compiled, all parts of the partial class are merged into a single class definition.
  • The partial class allows developers to work on different parts of a class independently without interfering with each other.
  • Methods, properties, fields, and events can all be part of a partial class and defined across multiple files.
  • Partial methods are special methods that can be declared in a partial class but are not required to have an implementation in every part of the class. If not implemented, they are excluded from the final compiled class.
  • Partial classes do not have access to members of other classes unless explicitly referenced; the separation is for organization, not visibility.
  • Partial classes are often used in scenarios like code generation, serialization, or large project structures to manage complexity.



Tuples IN CSHARP:

  • A tuple is a data structure that can hold multiple values of different types.
  • Tuples are created using the Tuple class or with the newer syntax using the ValueTuple type, introduced in C# 7.0.
  • Tuples are commonly used to return multiple values from a method without needing a custom class or struct.
  • The tuple values can be of any type and are accessed using item1, item2, etc., or with named elements for better clarity.
  • Tuples can be declared with the syntax (type1 value1, type2 value2, ...), making it easier to group data.
  • Named tuples allow naming the elements of the tuple for improved readability. Example: (string Name, int Age) instead of (string, int).
  • Tuples are immutable, meaning once they are created, their values cannot be changed.
  • Tuples can be used in method signatures to return multiple values in a concise and readable way.
  • Tuples provide a more lightweight alternative to out parameters and are preferable when returning several values from a method.
  • Tuple deconstruction allows extracting individual values from a tuple into separate variables.
  • The ValueTuple type provides better performance than the Tuple class, as it avoids creating an object on the heap.
  • Tuples can be nested, allowing more complex data structures when necessary.
  • Equality comparisons are supported for tuples; two tuples are considered equal if all their corresponding elements are equal.
  • Tuples are commonly used for situations where you need a quick, temporary group of values without defining a full class or struct.



Var:
var is used to declare a variable while initializing it with a value, which is mandatory. The compiler infers the variable's type based on the assigned value at compile time. Once set, the type cannot be changed, ensuring type safety throughout the code. It also provides IntelliSense support, enhancing code completion and suggestions for a better developer experience. However, var cannot be used as a return type for methods. The variable var is a static type that facilitates compile-time type checking.



virtual Keyword in C#
In C#, the virtual keyword allows methods, properties, and indexers in a base class to be overridden in derived classes, facilitating polymorphism and extending class behavior.

The virtual keyword enables derived classes to provide specialized implementations for base class members. This applies to methods, properties, and indexers, allowing these elements to be customized in derived classes.

To override a virtual member in a derived class, use the override keyword. This new implementation will be used when the member is accessed through a base class reference.

The virtual keyword supports polymorphism, enabling overridden methods to be called dynamically based on the actual derived type at runtime.

Using the new keyword in a derived class hides, rather than overrides, the base class member. The base class implementation remains accessible through a base class reference, while the derived class member is used through a derived class reference.

Abstract methods are a type of virtual method that lack implementation in the base class and must be overridden in derived classes.

The sealed keyword can be used in a derived class to prevent further overriding of a method, finalizing it within that derived class.

While overriding methods introduces some performance overhead due to virtual method table lookups, this impact is generally minimal compared to the flexibility and extensibility provided by polymorphism.





Yield in C#:
The yield keyword in C# is powerful for creating custom iteration and stateful iteration without the need for temporary collections. Here are some key points about yield that can enhance your understanding of how it works and its implications:

yield return is used to return each element in the collection one at a time. It simplifies the implementation of an iterator by automatically managing the state and resuming execution where it left off.

yield break is used to terminate the iteration early, stopping the iteration process and exiting the iterator block.

Methods that use yield return or yield break are known as iterator methods. These methods return an IEnumerable or IEnumerable<T>. Properties can also use yield to provide custom enumeration.

yield supports deferred execution, meaning the iteration logic is not executed until the enumerator is actually iterated over. This can lead to performance improvements with large data sets or expensive operations.

The yield keyword preserves the state of iteration. Each call to the iterator method resumes from where it last left off, retaining state between calls.

While yield simplifies code and reduces the need for temporary collections, it's important to be aware of potential performance impacts. The overhead of managing state and deferred execution might affect performance in some scenarios.

When using yield, the C# compiler generates a state machine to manage the iteration process. This means the iteration logic is converted into a more complex stateful code internally, which can be useful to understand for performance tuning and debugging.

yield is supported in .NET Framework 2.0 and later versions, as well as in .NET Core and .NET 5/6+. Knowing its compatibility helps ensure that your code will work across different versions of .NET.


Example:
using System;
using System.Collections.Generic;

namespace YieldKeywordExample
{
    public class FibonacciGenerator
    {
        // Iterator method with yield return
        public IEnumerable<int> GenerateFibonacci(int count)
        {
            int a = 0, b = 1, c = 0;
            for (int i = 0; i < count; i++)
            {
                yield return a;
                c = a + b;
                a = b;
                b = c;
            }
        }

        // Iterator method with yield break
        public IEnumerable<int> GenerateLimitedFibonacci(int count, int maxValue)
        {
            int a = 0, b = 1, c = 0;
            for (int i = 0; i < count; i++)
            {
                if (a > maxValue)
                {
                    yield break; // Exit the iteration
                }
                yield return a;
                c = a + b;
                a = b;
                b = c;
            }
        }
    }

    class Program
    {
        static void Main()
        {
            FibonacciGenerator fibGen = new FibonacciGenerator();

            Console.WriteLine("Fibonacci Sequence:");
            foreach (var number in fibGen.GenerateFibonacci(10))
            {
                Console.WriteLine(number);
            }

            Console.WriteLine("\nLimited Fibonacci Sequence:");
            foreach (var number in fibGen.GenerateLimitedFibonacci(10, 20))
            {
                Console.WriteLine(number);
            }
        }
    }
}



Explanation:
yield return: Used to return each Fibonacci number one by one in the GenerateFibonacci method.
yield break: Stops the iteration in the GenerateLimitedFibonacci method when the value exceeds a maximum limit.
Deferred Execution: The Fibonacci sequences are generated on-demand as they are iterated over, not in advance.
Including these additional points provides a more comprehensive understanding of how yield works and its various applications and implications.




VALUE TYPE IN CSHARP:
Variables of value types directly contain their data. Examples of value types include bool, byte, sbyte, short, ushort, int, uint, long, ulong, float, double, decimal, char, structs (custom types defined with the struct keyword), and enumerations (types defined with the enum keyword).

Value types have the following key characteristics:

Storage: They are typically stored on the stack or inline in objects on the heap.
Copy Semantics: Assigning a value type to another variable creates a copy of the value. Changes to one variable do not affect the other.
Default Values: They have a default value, such as 0 for numeric types, false for bool, and '\0' for char.
Nullable Value Types: They can be made nullable using the Nullable<T> structure or the shorthand T? syntax, allowing them to represent undefined or absent values.

Examples of using value types:
int number = 42; // int is a value type
char letter = 'A'; // char is a value type
bool isTrue = true; // bool is a value type



REFERENCE TYPES IN CSHARP:
In C#, reference types store references to the actual data in memory rather than the data itself. They are allocated on the heap and initialized to null by default if not explicitly assigned.

Key reference types include:

Classes: Define objects with properties, methods, and events. Example: class Person { public string Name; }
Strings: Immutable sequences of characters. Example: string greeting = "Hello";
Delegates: Represent methods as first-class objects. Example: delegate void MyDelegate();
Arrays: Collections of elements of the same type. Example: int[] numbers = new int[5];
Interfaces: Define contracts that classes can implement. Example: interface IAnimal { void Speak(); }
Reference types have distinct characteristics:

Mutability: Objects can be modified if they are mutable, such as classes. Strings are immutable, meaning operations on them create new strings.
Reference Semantics: Assigning one reference type variable to another makes both variables point to the same object. Changes through one reference affect the object seen through the other.
Garbage Collection: The .NET runtime manages memory through garbage collection, which reclaims memory from objects no longer in use.
Reference types are managed on the heap, affecting their lifecycle and performance compared to value types, which are managed on the stack. Always initialize reference type variables before use and handle null values to avoid exceptions.



REF:

C#'s Ref Keyword Overview
• Ref is Used to pass a parameter by reference.
• It is Bidirectional, affecting original variable outside the method.
• It Must be explicitly declared in method definition and call.
• Ref initialize Variable before passing to the method.
• Changes to ref parameter persist after method call.
• It is Useful for modifying caller's variable or returning multiple values.


In C#, the ref keyword is used to pass a parameter by reference, meaning that any changes made to the parameter inside the method will affect the original variable outside the method. It is bidirectional. The ref keyword must be explicitly declared in both the method definition and the method call. The variable passed as a ref parameter must be initialized before it is passed to the method. Any changes made to the ref parameter inside the method persist after the method call. Using ref is useful when a method needs to modify the caller's variable or when returning multiple values from a method.




OUT in C#:
Variables passed as out parameters do not need to be initialized before being passed to the method.

The out keyword must be specified in both the method definition and the method call.

out parameters are intended for output only; the method must assign a value to them before it returns.

Changes to out parameters do not affect the original variable outside the method unless explicitly assigned within the method.

Previous values of out parameters are discarded; they must be assigned new values within the method.

Initializing an out parameter before passing it will lead to the initial value being ignored. The method must assign a new value, which can lead to confusion about the purpose of the parameter.

out parameters are unidirectional, meaning they are used solely for output from the method to the caller.

Commonly used for returning multiple values from a method.

Using out parameters can be slightly more efficient than returning complex types when only a few values need to be returned.


Out in C# is a keyword used to specify variables for output only, with changes not affecting the original variable outside the method unless explicitly assigned. Out parameters do not have retained values and can be initialized before passing, but this can cause confusion. They are commonly used for returning multiple values from a method and can be slightly more efficient than returning complex types for a few values.


The override keyword in C#:

The override keyword in C# is used to provide a new implementation for a method, property, or indexer that is declared as virtual or abstract in a base class. This allows derived classes to modify or extend the behavior of inherited members.


The overriding member must have the same signature as the member it overrides, including the name, return type, and parameter list. You use override to implement a new behavior for a base class method, property, or indexer.


You can use the base keyword within an overridden member to call the base class’s implementation, allowing you to extend or modify the existing behavior. The access modifier of the overriding member must be the same as or more accessible than the base class member. For example, if the base method is protected, the overriding method can be protected or public.


Abstract methods in a base class must be overridden in derived classes, as they provide no implementation in the base class. Additionally, you can use the sealed keyword in an overriding method to prevent further overriding in any subsequent derived classes.


The override keyword supports polymorphism, allowing method calls to be dynamically resolved at runtime based on the actual derived type. While overriding introduces a slight performance overhead due to virtual method table lookups, this is generally minimal compared to the benefits of increased flexibility and extensibility.


The new keyword can be used to hide a base class member rather than override it. Whether to use override or new depends on whether you want to replace or hide the base class functionality.




Polymorphism in C#:

Polymorphism is a concept in Object-Oriented Programming that allows objects of different classes to be treated as objects of a common base class. It enables a single interface to represent different underlying forms (data types). Polymorphism improves code flexibility and maintainability by allowing methods to operate on objects of different classes in a uniform way.


Types of Polymorphism:

Compile-Time Polymorphism (Static Binding):


Method Overloading: 

Creating multiple methods with the same name but different parameters (different types or numbers) in a class. Method overloading allows methods to handle various types of inputs and perform the same logical operation.


Example:

public class Printer

{

    public void Print(string message) { /* Print string */ }

    public void Print(int number) { /* Print integer */ }

}

Operator Overloading: Defining custom behavior for operators (e.g., +, -, *) for user-defined types. This allows you to use operators with classes in a way that makes sense for those classes.


Example:

public class ComplexNumber

{

    public int Real { get; set; }

    public int Imaginary { get; set; }


    public static ComplexNumber operator +(ComplexNumber c1, ComplexNumber c2)

    {

        return new ComplexNumber

        {

            Real = c1.Real + c2.Real,

            Imaginary = c1.Imaginary + c2.Imaginary

        };

    }

}


Run-Time Polymorphism (Dynamic Binding):


Method Overriding: 

Changing the functionality of a method inherited from a base class without altering its signature. The base class method must be marked with the virtual keyword, and the derived class method must use the override keyword.


Example:

public class Animal

{

    public virtual void Speak() { Console.WriteLine("Animal speaks"); }

}


public class Dog : Animal

{

    public override void Speak() { Console.WriteLine("Dog barks"); }

}

Abstract Classes and Methods: Abstract classes cannot be instantiated and are used to provide a base for other classes. They can contain abstract methods, which must be overridden in derived classes.


Example:

public abstract class Shape

{

    public abstract void Draw();

}


public class Circle : Shape

{

    public override void Draw() { Console.WriteLine("Drawing Circle"); }

}

Interfaces: Interfaces define a contract that classes must implement, allowing for polymorphic behavior by ensuring that different classes adhere to the same set of method signatures.


Example:



public interface IDrawable

{

    void Draw();

}


public class Rectangle : IDrawable

{

    public void Draw() { Console.WriteLine("Drawing Rectangle"); }

}



Keywords:


Virtual: Used in the base class to declare a method that can be overridden.

Override: Used in the derived class to provide a new implementation of a method declared as virtual in the base class.

Base Class Method Invocation:


Base Keyword: Use the base keyword to call the base class method from the derived class if needed.

Common Pitfalls:


Virtual Methods: Ensure the base class method is marked as virtual to allow overriding.

Casting Issues: Be cautious with type casting when working with polymorphic objects.




Inheritance IN CSHARP:

  • Inheritance is a fundamental object-oriented programming concept that allows a class to inherit members (fields, methods, properties) from another class.
  • The base class (or parent class) provides the common functionality.
  • The derived class (or child class) inherits from the base class using the : baseClass syntax.
  • The derived class can extend or override the functionality of the base class.
  • Method overriding is achieved using the override keyword in the derived class, and it must match the method signature in the base class.
  • The base class constructor can be called from the derived class using the base keyword.
  • Access modifiers (e.g., public, protected, private) determine the visibility of inherited members in the derived class.
  • Protected members are accessible within the class itself and by derived classes, but not outside of them.
  • A derived class can also have additional members that are not present in the base class.
  • The virtual keyword in the base class indicates that a method can be overridden by derived classes.
  • Polymorphism allows a derived class to be used in place of a base class, providing flexibility in method execution.
  • Base class methods can be invoked from the derived class using the base keyword if needed.
  • Single inheritance is supported in C#, meaning a class can inherit from only one base class, but it can implement multiple interfaces.
  • Abstract classes serve as a blueprint for derived classes and cannot be instantiated directly. They can contain abstract methods, which must be implemented in derived classes.
  • Interfaces allow multiple inheritance of behavior, enabling classes to implement multiple interfaces, but they don’t provide implementation details.


In C#, the concept of immutability refers to the property of an object whose state cannot be modified after it has been created. Immutable objects are often used to ensure that data remains consistent and reliable throughout an application, especially in multithreaded environments.

Here are some key points about immutability in C#:

1. Immutable Types in .NET
Strings: In C#, strings are immutable. Once a string object is created, its value cannot be changed. Any operation that seems to modify a string actually creates a new string object.

Tuples: Tuples introduced in C# 7.0 are also immutable. Once a tuple is created, its values cannot be changed.

Record Types: Starting with C# 9.0, you can use record types, which are designed to be immutable by default. Records automatically generate read-only properties and provide value-based equality semantics.

2. Creating Immutable Types
To create an immutable class in C#, follow these guidelines:

1. Use Read-Only Fields: Define fields as readonly to ensure they cannot be modified after initialization.

2. Provide Only Getters for Properties: Make properties read-only by providing only getters without setters.

3. Initialize Fields in Constructor: Set values in the constructor, ensuring that all fields are initialized at object creation.

4. Avoid Exposing Mutable References: If your class contains references to mutable objects (like lists or arrays), make sure to provide only read-only access to those references or to clone them when returning.

Example of an Immutable Class
Here’s a simple example of an immutable class in C#:

public class ImmutablePerson
{
    public string Name { get; }
    public int Age { get; }

    public ImmutablePerson(string name, int age)
    {
        Name = name;
        Age = age;
    }
}
In this example:

The Name and Age properties have only getters, so their values cannot be changed after the ImmutablePerson object is created.
The ImmutablePerson class is immutable because its state cannot be modified after construction.
Using Records for Immutability
Records in C# make creating immutable types easier and provide additional features like value equality and convenient syntax:



public record Person(string Name, int Age);
In this example, Person is an immutable type with automatic properties and built-in support for value equality. You can create a new Person instance and it will be immutable:



var person = new Person("Alice", 30);
You can also use with expressions to create modified copies:



var olderPerson = person with { Age = 31 };
Benefits of Immutability
Thread Safety: Immutable objects are inherently thread-safe because their state cannot be changed after creation.
Simplicity: Immutable objects often simplify reasoning about code because you don’t have to consider how objects might be modified elsewhere.
Predictable Behavior: Since the state does not change, the behavior of immutable objects is more predictable and easier to debug.
Summary
Immutability in C# can be achieved through various means like immutable classes, records, and immutable data structures. Using immutable types can enhance the safety and clarity of your code, particularly in concurrent or complex systems.



OOPS:
Object-Oriented Programming (OOP) is a programming paradigm that structures software design around objects, which encapsulate both data and methods. In C#, OOP facilitates the creation of modular, reusable, and maintainable code by modeling real-world entities and their behaviors.
By organizing code into classes and objects, OOP leverages key principles such as encapsulation, inheritance, polymorphism, and abstraction to enhance flexibility, reduce redundancy, and improve code management.

OOP offers several advantages:
It provides a clear structure for programs.
It adheres to the DRY (Don't Repeat Yourself) principle, making code easier to maintain, modify, and debug.
It enables the creation of reusable applications with less code and shorter development times.
In OOP, a class serves as a template for creating objects, while an object is an instance of a class. When objects are created, they inherit all the variables and methods defined in their class.


Class:
A class defines the structure of an object, including variables (or attributes) for storing data and methods (or functions) to perform operations on that data. It is a fundamental building block in object-oriented programming (OOP), providing a template for creating objects and encapsulating both data and behavior. By using classes, developers can create well-structured, maintainable, and reusable code.

Object:
In C#, an object is an instance of a class, created using the `new` keyword. 
It represents the class's structure, including its data and methods. Each object has a unique state and behavior, with its own fields and methods as defined by the class. The `new` keyword allocates memory for the object and returns a reference that allows interaction with its data and methods.


Constructors in C#
A constructor is a special method in a class that is automatically invoked when an instance of the class is created. Its primary purpose is to initialize the object's data and set up any necessary state before the object is used.

Key points about constructors:

A constructor has the same name as the class and does not have a return type, not even void.
Constructors are used to set initial values for the object’s fields or to perform any setup operations needed before the object is used.
Constructors are invoked during object creation, allowing for proper initialization of the object.
Multiple constructors can be defined within a class, each with different parameters. This feature, known as constructor overloading, provides flexibility in object creation.
Types of Constructors:

Default Constructor: A parameterless constructor provided automatically by C# if no constructors are explicitly defined in the class. It initializes the object with default values. If you define any other constructors, the default constructor is no longer provided automatically.

Parameterized Constructor: A constructor that accepts parameters, allowing for customized initialization values when creating an object. This enables more control over the initial state of an object.

Static Constructor: A constructor used to initialize static members of the class. It cannot take parameters and is called automatically when the class is first accessed. This constructor is useful for setting up any static data or performing actions that need to occur only once per class, rather than per instance.

Primary Constructor (Introduced in C# 9.0): 
A streamlined syntax for defining constructors that initializes properties directly within the constructor's parameters. This feature reduces boilerplate code by combining property declarations and initialization in a single statement.
Benefits: Primary constructors simplify object creation by reducing redundancy, especially for classes with simple initialization needs.

Primary Constructor Example:
public class Person(string name, int age)
{
    public string Name { get; } = name;
    public int Age { get; } = age;
}




Access modifiers:
Access modifiers in C# are used to control the visibility and accessibility of classes, methods, and other members. They play a crucial role in encapsulating data and protecting the integrity of an object’s state.

public:

Purpose: Allows unrestricted access to the class members from any part of the program, including other classes and assemblies.
Use Case: Use public for members that need to be accessible by other classes, such as methods or properties that provide essential functionality or data.
Example
public class Person
{
    public string Name { get; set; }
    public void Introduce()
    {
        Console.WriteLine($"Hello, my name is {Name}.");
    }
}



private:
Purpose: Restricts access to the class members so they can only be accessed within the same class. This ensures that internal data and operations are hidden from outside interference.
Use Case: Use private for internal data and helper methods that should not be exposed to other classes. It helps maintain the integrity of the object by controlling how its data is accessed and modified.
Example:
public class BankAccount
{
    private decimal balance;

    public void Deposit(decimal amount)
    {
        if (amount > 0)
            balance += amount;
    }

    public decimal GetBalance()
    {
        return balance;
    }
}



protected:
Purpose: Allows access to members from within the same class and from derived classes. It’s useful for creating class hierarchies where child classes need to access or modify base class members.
Use Case: Use protected when you want to expose data or methods to subclasses but not to other classes or external code.
Example:
public class Animal
{
    protected string species;

    public void SetSpecies(string species)
    {
        this.species = species;
    }
}

public class Dog : Animal
{
    public void DisplaySpecies()
    {
        Console.WriteLine($"This is a {species}."); // Accessible due to protected
    }
}



internal:
Purpose: Restricts access to members so they can only be accessed within the same assembly. This is useful for hiding implementation details from other assemblies while exposing them within the assembly.
Use Case: Use internal for classes and members that are intended to be used only within the same project or library.
Example:
internal class InternalHelper
{
    internal void Help()
    {
        Console.WriteLine("Helping with internal tasks.");
    }
}



protected internal:
Purpose: Combines protected and internal access levels, allowing access within the same assembly and in derived classes from any assembly.
Use Case: Use protected internal when you want to allow access to derived classes and classes within the same assembly, but not from external assemblies.
Example:
public class BaseClass
{
    protected internal string data;

    public BaseClass()
    {
        data = "Accessible within the same assembly or by derived classes.";
    }
}

public class DerivedClass : BaseClass
{
    public void ShowData()
    {
        Console.WriteLine(data); // Accessible due to protected internal
    }
}



private protected:
Purpose: Restricts access to members so they are only accessible within the containing class and by derived classes in the same assembly. This is a more restrictive combination of private and protected.
Use Case: Use private protected to limit access to derived classes within the same assembly, providing a high level of encapsulation while allowing some flexibility for inheritance.
Example:
public class BaseClass
{
    private protected string restrictedData;

    public BaseClass()
    {
        restrictedData = "Accessible only within this assembly and by derived classes.";
    }
}

public class DerivedClass : BaseClass
{
    public void ShowRestrictedData()
    {
        Console.WriteLine(restrictedData); // Accessible due to private protected
    }
}



Access modifiers in C# are essential for controlling how and where class members can be accessed. They help maintain encapsulation by defining clear boundaries around data and functionality. By choosing the appropriate access modifier, you ensure that your code remains secure, maintainable, and understandable.




Properties in C#:
In C#, properties are members of a class or struct that offer a controlled mechanism to read, write, or compute the values of private fields. They combine the simplicity of fields with the flexibility of methods, allowing data to be exposed and managed securely and efficiently. By using properties, you can encapsulate data, enforce validation, and enhance maintainability and security, leading to a more robust object-oriented design.

Components of a Property
1. Accessor Methods:

Getter (get): Retrieves the value of the property.
Setter (set): Assigns a value to the property.

public class Person
{
    private string name; // Private field

    public string Name   // Property
    {
        get { return name; }    // Getter
        set { name = value; }   // Setter
    }
}



2. Auto-Implemented Properties:

These simplify property declaration by eliminating the need for a private field. The compiler automatically creates a backing field.
Example:
public class Person
{
    public string Name { get; set; }  // Auto-implemented property
    public int Age { get; set; }      // Auto-implemented property
}


3. Read-Only and Write-Only Properties:

Read-Only: Only has a getter and cannot be set from outside the class.
Write-Only: Only has a setter and cannot be read from outside the class.
Examples:
public class Person
{
    private string name;
    private int birthYear;

    // Read-only property
    public string Name
    {
        get { return name; }
    }

    // Write-only property
    public int BirthYear
    {
        set { birthYear = value; }
    }

    // Constructor to set Name
    public Person(string name)
    {
        this.name = name;
    }
}



4. Expression-bodied Properties:

A shorthand syntax for properties with a single expression in the getter or setter.
Example:
public class Circle
{
    private double radius;

    public double Radius
    {
        get => radius;  // Expression-bodied getter
        set => radius = value;  // Expression-bodied setter
    }

    public double Diameter => 2 * radius;  // Read-only property with expression-bodied getter
}




5. Property with Logic:

Properties can include logic within the getter and setter to enforce constraints or perform additional operations.


public class BankAccount
{
    private decimal balance;

    public decimal Balance
    {
        get { return balance; }
        set
        {
            if (value < 0)
                throw new ArgumentException("Balance cannot be negative");
            balance = value;
        }
    }
}



6. Indexers:

Special properties that allow instances of a class to be indexed like arrays. Indexers can have different access levels for getters and setters.
Example:
public class PhoneBook
{
    private Dictionary<string, string> contacts = new Dictionary<string, string>();

    public string this[string name]
    {
        get
        {
            if (contacts.TryGetValue(name, out var number))
                return number;
            return "Contact not found";
        }
        set
        {
            contacts[name] = value;
        }
    }
}




Benefits of Using Properties
Encapsulation:
Properties allow for control over how data is accessed and modified, providing a way to enforce validation rules and maintain encapsulation.

Readability and Maintenance:
Properties improve code readability by providing a clear and consistent way to access and modify class data. They also make it easier to update the implementation later without changing the class's public interface.

Flexibility:
Properties can be used to compute values dynamically (read-only properties) or to implement complex logic (getters and setters) while maintaining a clean and intuitive syntax.




'as' Operator:
The as operator in C# provides a way to perform safe type casting, which avoids exceptions and allows you to handle cases where the cast might fail. It is particularly useful with reference types and nullable value types.
The as operator is a handy tool for working with types dynamically and helps in maintaining cleaner and safer code by avoiding unnecessary exceptions.

Safe Casting: The as operator attempts to cast an object to a specified type. If the cast is not possible, it returns null instead of throwing an exception.
Reference Types and Nullable Types: The as operator works with reference types and nullable types (e.g., int?). It does not work with non-nullable value types directly. To use as with value types, you need to use nullable types, like int?.
Avoiding Exceptions: Using as is preferable in situations where you are unsure of the object's type and want to avoid the overhead of handling exceptions like InvalidCastException.

Limitations
Non-nullable Value Types: You cannot use as to cast directly to non-nullable value types like int or double. For such cases, you must use explicit casting and handle possible exceptions or use the is keyword combined with conditional logic.

Performance Considerations: While using as is generally efficient, be mindful of performance impacts in critical code paths where type checking might be frequent.


Examples
Casting to Reference Type:

object obj = "Hello, World!";
string str = obj as string;  // str is "Hello, World!" because obj is a string
Casting to Nullable Type:


object obj = 123;
int? number = obj as int?;  // number is 123, since obj can be cast to int?

Handling Failure:

object obj = 123;
string str = obj as string;  // str is null because obj is not a string
if (str == null)
{
    Console.WriteLine("Cast failed.");
}


Example:
object obj = "Hello, World!";
string str = obj as string;  // Safe cast; str will be "Hello, World!"

Explanation:
The as operator helps preserve the original object’s type and allows checking if the cast is possible without altering the original object.










Encapsulation:
Encapsulation is the principle of bundling data (fields) and methods (functions) into a single unit, known as a class, and restricting direct access to some of its components. This is done using access modifiers to control visibility and access levels.

Encapsulation is a fundamental concept in object-oriented design that enhances code security, maintainability, and modularity. By hiding the internal state of an object and requiring interaction through public methods, encapsulation protects data integrity and provides a clear, controlled interface for class interaction.

Encapsulation improves code modularity by grouping related data and methods into a single class. This setup minimizes the impact of changes, ensuring that modifications to one part of the class have little to no effect on other parts of the program.
Encapsulation facilitates easier maintenance and updates by isolating the internal implementation of a class. Changes to how a class works internally do not affect other parts of the application that use the class, reducing the risk of unintended side effects.


The access modifiers used to implement encapsulation are:

Private: Restricts access to members of the class. Only the class itself can access its private fields and methods.
Public: Allows access to members from any part of the program.
Protected: Allows access to members from within the class and its derived classes.
Internal: Allows access to members within the same assembly.
Protected Internal: Allows access to members from within the same assembly or from derived classes.




Records are a special kind of reference type introduced in C# 9.0, designed to simplify the creation of immutable data structures with value-based equality.

By default, records are immutable. Once a record is created, its properties cannot be modified, ensuring that the values remain constant throughout the object's lifecycle.

Records automatically implement value-based equality. This means that two records are considered equal if all their properties have the same values, rather than comparing their memory addresses.

Records support deconstruction, which allows you to easily extract values from a record into separate variables. This feature makes it straightforward to work with individual components of the record.

The with expression in records enables the creation of a new instance based on an existing record, with some properties modified. This feature provides a convenient way to update records while maintaining their immutability.

Records can be defined using positional syntax, which simplifies the creation of data containers by allowing properties and their initial values to be declared directly in the constructor.

Records can also participate in inheritance. You can create derived records and define abstract records. However, it is essential to maintain immutability in derived types to align with the primary purpose of records.

Starting with C# 10, you can define record structs. Unlike record classes, record structs are value types and are stack-allocated. They offer similar features to record classes but are designed to be more lightweight and efficient in specific scenarios.

While records automatically handle value-based equality and hash code generation, you can override these methods if custom behavior is required. However, this is typically unnecessary for standard use cases.

Properties in records are inherently init-only, meaning they can only be set during object initialization. This feature supports immutability by preventing modifications after the object is created.

Records can also be defined with traditional property syntax if positional syntax is not suitable. This flexibility allows for more complex records and additional customization options.


Records for Author and Book
Author Record:


Example:
public record Author(string Name, string Nationality);
Explanation: Author is a record with two properties: Name and Nationality. Records in C# are immutable and provide built-in support for value-based equality.
Book Record:


Example:
public record Book(string Title, Author Author, int YearPublished);
Explanation: Book is a record with three properties: Title, Author, and YearPublished. The Author property is of type Author, showing that records can contain other records.
Creating Instances

Example:
var author1 = new Author("George Orwell", "British");
var book1 = new Book("1984", author1, 1949);
Explanation: Here, author1 is an instance of Author, and book1 is an instance of Book using author1 as its Author.
Comparing Instances

Example:
var author2 = new Author("George Orwell", "British");
var book2 = new Book("1984", author2, 1949);

Console.WriteLine(book1 == book2); // True
Explanation: Records use value-based equality. book1 and book2 are considered equal if all their properties, including nested properties (like Author), are equal. Thus, book1 and book2 are equal because they have the same values for all properties.
Deconstruction

Example:
var (title, author, yearPublished) = book1;
Console.WriteLine($"Title: {title}, Author: {author.Name}, Year Published: {yearPublished}");
// Output: Title: 1984, Author: George Orwell, Year Published: 1949
Explanation: Deconstruction allows you to extract values from a record into individual variables. For book1, title, author, and yearPublished are extracted and printed.
Creating a New Record with Modified Properties

Example:
var updatedBook = book1 with { YearPublished = 1950 };
Console.WriteLine(updatedBook); // Book { Title = 1984, Author = Author { Name = George Orwell, Nationality = British }, YearPublished = 1950 }
Explanation: The with expression creates a new instance of the record with some properties changed. Here, updatedBook is a new instance of Book with the YearPublished property updated, while other properties remain the same.
Record Struct for Shelf Position

Example:
public readonly record struct ShelfPosition(int Row, int Column);
Explanation: ShelfPosition is a record struct, a value type. It provides immutability and value-based equality, similar to record classes but with value type semantics.

Example:
var position1 = new ShelfPosition(3, 15);
var position2 = new ShelfPosition(3, 15);

Console.WriteLine(position1 == position2); // True
Explanation: Value-based equality for record structs means that position1 and position2 are considered equal if their Row and Column values are the same.
Overriding Equality Methods

Example:
public record DetailedBook(string Title, Author Author, int YearPublished)
{
    public override bool Equals(object? obj)
    {
        if (obj is DetailedBook other)
        {
            return Title == other.Title && Author == other.Author && YearPublished == other.YearPublished;
        }
        return false;
    }

    public override int GetHashCode()
    {
        return HashCode.Combine(Title, Author, YearPublished);
    }
}
Explanation: Although records automatically provide value-based equality and GetHashCode implementations, you can override these methods if you need custom behavior. The example overrides Equals and GetHashCode to define how equality is determined for DetailedBook.
Record with Traditional Property Syntax

Example:
public record Publisher
{
    public string Name { get; init; }
    public string Address { get; init; }
}

var publisher = new Publisher
{
    Name = "Penguin Books",
    Address = "80 Strand, London"
};
Explanation: This example shows a record using traditional property syntax with init accessors, allowing for initialization only during object creation. This is useful for more complex scenarios where records have more intricate initialization requirements.
Summary
Records in C# are immutable, provide value-based equality, and support deconstruction.
Record Structs are value types with similar immutability and equality features.
Deconstruction and the with expression simplify working with records and making modifications.
Equality methods can be overridden if custom behavior is required.
Traditional property syntax in records offers flexibility for complex scenarios.
These features make records a powerful and convenient way to handle immutable data in C#.






^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Example:

define a record for a book and an author.
public record Author(string Name, string Nationality);

public record Book(string Title, Author Author, int YearPublished);


explanation:
Author is a record with properties Name and Nationality.
Book is a record with properties Title, Author, and YearPublished.



Create instances of the Author and Book records.
var author1 = new Author("George Orwell", "British");
var book1 = new Book("1984", author1, 1949);

Compare two instances of the Book record.
var author2 = new Author("George Orwell", "British");
var book2 = new Book("1984", author2, 1949);

Console.WriteLine(book1 == book2); // True, as all properties are the same
explanation:
Records use value-based equality, so two Book records are considered equal if all their properties, including nested properties like Author, are equal.

Extract values from a Book record using deconstruction.
var (title, author, yearPublished) = book1;
Console.WriteLine($"Title: {title}, Author: {author.Name}, Year Published: {yearPublished}");
// Output: Title: 1984, Author: George Orwell, Year Published: 1949



Create a new Book record based on an existing one with some properties changed.
var updatedBook = book1 with { YearPublished = 1950 };
Console.WriteLine(updatedBook); // Book { Title = 1984, Author = Author { Name = George Orwell, Nationality = British }, YearPublished = 1950 }




Define a record struct to represent a library shelf position.
public readonly record struct ShelfPosition(int Row, int Column);

var position1 = new ShelfPosition(3, 15);
var position2 = new ShelfPosition(3, 15);

Console.WriteLine(position1 == position2); // True, as both Row and Column are the same


explanation:
ShelfPosition is a record struct, which is a value type.

Override equality methods if needed (though it’s usually handled automatically).
public record DetailedBook(string Title, Author Author, int YearPublished)
{
    public override bool Equals(object? obj)
    {
        if (obj is DetailedBook other)
        {
            return Title == other.Title && Author == other.Author && YearPublished == other.YearPublished;
        }
        return false;
    }

    public override int GetHashCode()
    {
        return HashCode.Combine(Title, Author, YearPublished);
    }
}



Define a record using traditional property syntax for more complex scenarios.
public record Publisher
{
    public string Name { get; init; }
    public string Address { get; init; }
}

var publisher = new Publisher
{
    Name = "Penguin Books",
    Address = "80 Strand, London"
};



In this example:

Publisher uses traditional property syntax.
Properties are immutable due to the init accessor.
Summary
This example demonstrates how records can be used to model real-world scenarios with various features:

Immutability: Ensured by default in records.
Value-Based Equality: Records use value-based equality to compare instances.
Deconstruction: Allows for easy extraction of values.
With Expression: Facilitates creation of modified copies of records.
Record Structs: Provides value-type semantics with similar features.
Custom Equality: Customizing equality and hash code if needed.
Traditional Property Syntax: Offers flexibility for more complex records.
This example should give you a well-rounded understanding of how to work with C# records in practical scenarios.



Sealed Class vs. Abstract Class IN CSHARP:

Sealed Class:

  • A sealed class cannot be inherited by any other class.
  • A sealed class is declared using the sealed keyword.
  • It is used to prevent further inheritance and ensures that no class can extend it.
  • Sealed classes are typically used when the class is complete and doesn't need to be modified or extended.
  • Sealed classes can be instantiated, unlike abstract classes.
  • They can contain fully implemented methods, properties, and fields.
  • Performance: Sealed classes can improve performance because the compiler knows the class won’t be inherited, allowing optimizations like method inlining.

Abstract Class:

  • An abstract class cannot be instantiated directly; it must be inherited by other classes.
  • It is declared using the abstract keyword.
  • Abstract classes can contain both abstract methods (without implementation) and fully implemented methods.
  • Derived classes are required to implement the abstract methods unless the derived class is also abstract.
  • Abstract classes provide a blueprint for other classes to follow, enforcing a common structure.
  • They are useful for creating a common base with shared functionality but requiring specific implementation in derived classes.
  • Abstract classes can contain constructors, fields, properties, and events.

Key Differences:

  • A sealed class cannot be inherited, whereas an abstract class is specifically designed to be inherited.
  • A sealed class can be instantiated, while an abstract class cannot.
  • Abstract classes may contain abstract methods that require derived classes to provide implementations, while sealed classes cannot have abstract methods.



Extension IN CSHARP:

  • Extension methods allow you to add new functionality to existing types without modifying their source code.
  • They are defined as static methods in static classes, but they are called as if they were instance methods on the type being extended.
  • Extension methods use the this keyword in their first parameter to specify the type they are extending.
  • The namespace of the extension method must be imported for the method to be available to the class being extended.
  • Extension methods can be called like regular instance methods on objects of the extended type.
  • They do not modify the original type or class; they provide additional functionality.
  • Extension methods are most commonly used for adding functionality to interfaces, third-party libraries, or built-in types that you can't modify directly.
  • They are invisible to the class being extended, meaning the class does not know about the extension method.
  • LINQ (Language Integrated Query) methods, like Where(), Select(), are examples of extension methods.
  • Overloading extension methods with different signatures is possible, but you must avoid name conflicts with existing methods.
  • Static imports are required for extension methods, so their namespace must be included via using at the top of your file.
  • Extension methods cannot override existing methods in the extended type.


Fields vs. Properties in Csharp


Fields:
Direct data storage.
Accessed directly.
Less flexible for validation.

Properties:
Provide controlled access to fields.
Use get and set accessors.
Allow for validation and additional logic.




Tuples
Definition: Data structures that store multiple values in a single object.
Syntax: Created using parentheses:
Example:
  var tuple = (1, "Hello", 3.14);

Features:
- Can have named elements for clarity:
Example:
    var person = (Name: "Alice", Age: 30);

- Useful for returning multiple values from methods.


String & StringBuilder
String:
- Immutable sequence of characters. Once created, its value cannot be changed.
- Example:
Example:
    string greeting = "Hello, World!";

  
StringBuilder:
- Mutable and designed for efficient string manipulation.
- Ideal for scenarios where the string value changes frequently (e.g., concatenation).
- Example:
Example:
    var sb = new StringBuilder();
    sb.Append("Hello");
    sb.Append(" World!");
    string result = sb.ToString(); // "Hello World!"



Record
      A reference type introduced in C# 9 for immutable data models.

Features:
- Automatically provides value-based equality, simplifying data handling.
- Syntax:
Example:
    public record Person(string Name, int Age);

- Ideal for data transfer objects (DTOs) and similar use cases.


Reference and Value Types
Value Types:
- Stored on the stack; each variable holds its own data.
- Examples: `int`, `float`, `struct`.
  
Reference Types:
- Stored on the heap; variables store references to the data.
- Examples: `class`, `string`, `array`.
- Multiple variables can reference the same object.



`typeof` and `nameof`
`typeof`:
- Returns the `System.Type` object for a type.
- Example:
Example:
    Type typeInfo = typeof(string);


`nameof`:
- Returns the name of a variable, type, or member as a string.
- Useful for refactoring and avoiding hard-coded strings.
- Example:
Example:
    string name = nameof(Person); // "Person"



IQueryable in CSharp:
IQueryable is used for querying databases with LINQ. It executes queries only when the data is needed, employing deferred execution. This allows for filtering and condition checking at the database level rather than in memory, making it efficient for large datasets. Additionally, IQueryable supports LINQ methods that translate directly into queries for the data source, optimizing performance. It is best suited for querying large datasets from a database.

Coding:
The sample of IQueryable in the provided code is specifically found in the GetEmployeesAsync method of the EmployeeRepository class. Here's the key portion that demonstrates its usage:

Sample of IQueryable in GetEmployeesAsync

Example:
public async Task> GetEmployeesAsync(int pageNumber, int pageSize)
{
var employees = await _context.Employees
.OrderByDescending(emp => emp.Salary) // IQueryable method
.Skip((pageNumber - 1) * pageSize) // IQueryable method
.Take(pageSize) // IQueryable method
.ToListAsync(); // Executes the query

return employees;
}


Breakdown of IQueryable Usage

1. _context.Employees: This is an IQueryable, representing the collection of employees in the database.

2. OrderByDescending(emp => emp.Salary): This method call adds sorting to the query. The IQueryable allows you to build the query without executing it immediately.

3. Skip((pageNumber - 1) * pageSize): This method is used to skip a specific number of records based on pagination.

4. Take(pageSize): This method specifies how many records to take after skipping.

5. ToListAsync(): This executes the query against the database, returning the results as a list. It's important to note that until this line is reached, the query has not been executed; this is the concept of deferred execution with IQueryable.

Summary

This method showcases how to leverage IQueryable for building complex queries that are executed against a database, allowing for efficient data retrieval with features like sorting and pagination. Let me know if you need further clarification or additional examples!



using System;
using System.Collections.Generic;
using System.Linq;

public class Employee
{
public int Id { get; set; }
public string Name { get; set; }
}

public class Program
{
public static void Main()
{
using (var context = new ApplicationDbContext())
{
IQueryable employees = context.Employees; // Explicitly IQueryable

// Checking the type at runtime
Console.WriteLine(employees.GetType()); // Outputs: System.Linq.IQueryable1[YourNamespace.Employee]
}
}
}




Generics in C#

Generic Classes:
A generic class is a class that can work with any data type. You define a placeholder in the class definition and specify the actual type when you create an instance of the class.

Example:
public class Box
{
private T content;

public void SetContent(T content)
{
this.content = content;
}

public T GetContent()
{
return content;
}
}

Usage:
Example:
Box intBox = new Box();
intBox.SetContent(123);
int content = intBox.GetContent(); // content is 123

Box stringBox = new Box();
stringBox.SetContent("Hello, Generics!");
string message = stringBox.GetContent(); // message is "Hello, Generics!"


2. Generic Methods:
Generic methods allow you to define a method with one or more type parameters. This is useful when the method needs to operate on various types but should be type-safe.

Example:
public class Utilities
{
public T Max(T a, T b) where T : IComparable
{
return a.CompareTo(b) > 0 ? a : b;
}
}

Usage:
Example:
Utilities utilities = new Utilities();
int maxInt = utilities.Max(10, 20); // maxInt is 20
string maxString = utilities.Max("apple", "orange"); // maxString is "orange"


3. Generic Interfaces:
Similar to generic classes, you can define interfaces with type parameters. This is useful for creating type-safe collections or other types that work with multiple data types.

Example:
public interface IContainer
{
void Add(T item);
T Get(int index);
}

public class StringContainer : IContainer
{
private List items = new List();

public void Add(string item)
{
items.Add(item);
}

public string Get(int index)
{
return items[index];
}
}


4. Constraints:
You can place constraints on the type parameters to ensure they meet certain criteria. Common constraints include:

- `where T : struct`: Ensures that T is a value type.
- `where T : class`: Ensures that T is a reference type.
- `where T : new()`: Ensures that T has a parameterless constructor.
- `where T : BaseClass`: Ensures that T inherits from `BaseClass`.
- `where T : IInterface`: Ensures that T implements `IInterface`.

Example:
public class Repository where T : class, new()
{
public T CreateInstance()
{
return new T(); // Requires T to have a parameterless constructor
}
}



Generic Collections:
The .NET framework provides several generic collections that are commonly used, such as `List`, `Dictionary`, and `Queue`.

Example:
List numbers = new List { 1, 2, 3, 4, 5 };
Dictionary ages = new Dictionary
{
{ "Alice", 30 },
{ "Bob", 25 }
};


Advantages of Using Generics:
- Type Safety: Generics provide compile-time type checking, which reduces runtime errors.
- Code Reusability: You can write code that works with any data type, avoiding duplication.
- Performance: Generics can reduce the need for boxing and unboxing, which can improve performance.

Generics are a cornerstone of modern C# programming, enabling developers to write more efficient, flexible, and maintainable code.



Virtual VS abstract in c#:

In C#, both virtual and abstract are keywords used to define methods and properties in a class, primarily for implementing polymorphism in object-oriented programming. However, they serve different purposes:

Virtual

- Definition: A virtual method is one that can be overridden in any derived class. It provides a default implementation but allows derived classes to provide their own implementation if desired.

- Usage: Use the virtual keyword in the base class when you want to allow derived classes to modify the behavior of a method.


Example:

public class BaseClass

{

public virtual void Display()

{

Console.WriteLine("Display from BaseClass");

}

}


public class DerivedClass : BaseClass

{

public override void Display()

{

Console.WriteLine("Display from DerivedClass");

}

}



Abstract

- Definition: An abstract method does not provide an implementation in the base class. Instead, it forces any derived class to provide an implementation.

- Usage: Use the abstract keyword in a class when you want to define a method that must be implemented by all derived classes.

Example:

public abstract class AbstractClass

{

public abstract void Display();

}


public class ConcreteClass : AbstractClass

{

public override void Display()

{

Console.WriteLine("Display from ConcreteClass");

}

}



Key Differences

1. Implementation:

- virtual methods have a default implementation.

- abstract methods do not have an implementation in the base class.


2. Class Type:

- A class with a virtual method can be instantiated.

- An abstract class cannot be instantiated directly.


3. Override Requirement:

- Derived classes can choose to override virtual methods.

- Derived classes must override abstract methods.


Summary

- Use virtual when you want to provide a default behavior that can be overridden.

- Use abstract when you want to ensure that derived classes provide their own implementation.


Both keywords play a crucial role in defining flexible and reusable code structures in C#.

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