C# Fundamentals

1. 🔴 What is C#, and what are its main features?

C# (C-Sharp) is a modern, object-oriented, strongly typed programming language developed by Microsoft.

It is mainly used to develop Web Applications, Web APIs, Desktop Applications, Cloud Applications, and Enterprise Applications.

Main Features:

1. Object-Oriented: Supports Encapsulation, Inheritance, Polymorphism, and Abstraction.

2. Strongly Typed: Checks data types to prevent type-related errors.

3. Automatic Memory Management: Garbage Collector (GC) automatically manages managed memory.

4. Platform Independent: Modern .NET applications can run on Windows, Linux, and macOS.

5. Exception Handling: Uses try, catch, and finally to handle errors.

6. Async Programming: Supports async and await for asynchronous operations.

Simple Example:

Console.WriteLine("Hello World");

Interview Key Point: C# is a strongly typed, object-oriented programming language used to build applications on the .NET platform.

2. 🔴 What is the difference between C# and .NET?

C# is a programming language, whereas .NET is a development platform used to build and run applications.

Simple Example:

• C#: We write application logic using C#.

• .NET: Provides the runtime and libraries required to execute the application.

Interview Key Point: C# is the language used to write code, while .NET provides the runtime, libraries, and tools to build and execute applications.

3. 🔴 What is CLR, and how does it execute C# code?

CLR (Common Language Runtime) is the execution engine of .NET. It is responsible for executing managed code.

How CLR Executes C# Code:

C# Source Code (.cs)
        |
        v
C# Compiler
        |
        v
IL Code (Intermediate Language)
        |
        v
CLR (.NET Runtime)
        |
        v
JIT Compiler
        |
        v
Native Machine Code
        |
        v
Execution

Main Responsibilities of CLR:

1. Memory Management: Allocates and manages managed memory.

2. Garbage Collection: Automatically releases memory occupied by unreachable managed objects.

3. Exception Handling: Supports handling runtime exceptions.

4. Type Safety: Helps prevent invalid type operations.

5. JIT Compilation: Converts IL code into native machine code during execution.

Interview Key Point: CLR is the .NET execution engine that manages code execution, memory, garbage collection, and exception handling. JIT converts IL into native machine code.

4. 🔴 What is the difference between managed and unmanaged code?

Managed Code: Code executed under the control of CLR is called managed code.

Unmanaged Code: Code executed outside the control of CLR is called unmanaged code.

Managed Code Example:

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

Here, the CLR manages the lifetime of Employee objects through garbage collection.

Unmanaged Code Example:

int* ptr = new int(100);
delete ptr;

Here, memory is allocated and explicitly released using C++.

Interview Key Point: Managed code runs under CLR with automatic memory management, while unmanaged code runs outside CLR and typically requires explicit resource management.

Quick Interview Revision

Important: Remember the execution flow: C# → Compiler → IL → CLR/JIT → Machine Code → Execution. This is a commonly asked .NET interview concept.