1. What is C#?

C# is a modern, object-oriented programming language developed by Microsoft. It is primarily used for developing Windows applications, web applications, and games using the .NET framework.

2. Setting Up Your Environment

1. Download and install the .NET SDK from Microsoft .NET.
2. Install Visual Studio or Visual Studio Code for development.
3. Verify installation by running dotnet --version in your terminal or command prompt.

3. Your First C# Program

Let’s write our first C# program:

using System;

class Program {
    static void Main() {
        Console.WriteLine("Hello, World!");
    }
}

Save this code as Program.cs, and run it using the following commands:

dotnet new console -o HelloWorldApp
cd HelloWorldApp
dotnet run

4. Variables and Data Types

C# supports various data types:

// Example:
int age = 25;
double pi = 3.14159;
char grade = 'A';
bool isStudent = true;
string name = "John Doe";

5. Conditional Statements

Conditional statements in C# include if, else if, and else.

// Example:
int num = 10;
if (num > 0) {
    Console.WriteLine("Positive number");
} else if (num == 0) {
    Console.WriteLine("Zero");
} else {
    Console.WriteLine("Negative number");
}

6. Loops

For Loop:

// Example:
for (int i = 0; i < 5; i++) {
    Console.WriteLine(i);
}

While Loop:

// Example:
int count = 0;
while (count < 5) {
    Console.WriteLine(count);
    count++;
}

7. Methods

using System;

class Program {
    static void Greet(string name) {
        Console.WriteLine($"Hello, {name}!");
    }

    static void Main() {
        Greet("Alice");
    }
}

8. Classes and Objects

using System;

class Person {
    public string Name { get; set; }
    public int Age { get; set; }

    public void Introduce() {
        Console.WriteLine($"Name: {Name}, Age: {Age}");
    }
}

class Program {
    static void Main() {
        Person person = new Person { Name = "Alice", Age = 25 };
        person.Introduce();
    }
}

9. Exception Handling

try {
    int result = 10 / 0;
} catch (DivideByZeroException ex) {
    Console.WriteLine($"Error: {ex.Message}");
} finally {
    Console.WriteLine("This block always executes.");
}

10. File Handling

// Writing to a file:
using System.IO;

class Program {
    static void Main() {
        File.WriteAllText("example.txt", "Hello, C#!");
    }
}

// Reading from a file:
using System;
using System.IO;

class Program {
    static void Main() {
        string content = File.ReadAllText("example.txt");
        Console.WriteLine(content);
    }
}

11. Collections in C#

using System;
using System.Collections.Generic;

class Program {
    static void Main() {
        List<string> names = new List<string> { "Alice", "Bob" };
        foreach (string name in names) {
            Console.WriteLine(name);
        }
    }
}

12. Multithreading in C#

using System;
using System.Threading;

class Program {
    static void Main() {
        Thread thread = new Thread(() => Console.WriteLine("Thread is running"));
        thread.Start();
    }
}