C#

A modern, object-oriented language for .NET applications, web services, and desktop development.

Getting Started

C# is a statically typed language developed by Microsoft for the .NET ecosystem. It is widely used for web APIs, desktop apps, cloud services, and game development.

Hello World

csharp

using System;

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

Run

bash

dotnet new console -o HelloApp
cd HelloApp
dotnet run

Types & Variables

C# has strong typing and supports both reference types and value types.

csharp

int count = 5;
string name = "RefMe";
bool isActive = true;
decimal price = 19.99m;

Nullable types

csharp

int? optionalNumber = null;
string? maybeText = null;

Classes & Methods

csharp

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

    public User(int id, string name)
    {
        Id = id;
        Name = name;
    }

    public void Greet()
    {
        Console.WriteLine($"Hello, {Name}!");
    }
}

Async & Await

Asynchronous programming uses Task and async methods.

csharp

using System.Threading.Tasks;

public async Task<string> FetchDataAsync()
{
    await Task.Delay(1000);
    return "Data loaded";
}

public async Task MainAsync()
{
    string result = await FetchDataAsync();
    Console.WriteLine(result);
}

LINQ

LINQ provides expressive queries over collections.

csharp

var numbers = new[] { 1, 2, 3, 4, 5 };
var even = numbers.Where(n => n % 2 == 0).ToList();
var names = new[] { "Alice", "Bob", "Charlie" };
var upper = names.Select(n => n.ToUpper());

.NET Tooling

The .NET CLI is used to build, run, and test projects.

bash

dotnet build
dotnet test
dotnet publish -c Release