C# Programming Introduction

What Is C#?

C# (pronounced “C sharp”) is a modern, multi-paradigm programming language from Microsoft. It is type-safe, object-oriented, and runs on .NET—used for web APIs, desktop apps, games (Unity), cloud services, and mobile apps.

C# program shape:
  using System;
  class Program {
    static void Main() { ... }
  }

Runs on:  .NET (cross-platform)
Created:  2000 by Anders Hejlsberg / Microsoft
Style:    compiled, managed, object-oriented

The C# compiler (Roslyn) and .NET runtime are open source under the .NET Foundation. This page is the gateway to the C# tutorial—practice topics such as strings, patterns, and interview programs have their own pages.

Why Learn C#?

C# pairs clear syntax with a large ecosystem. It is a strong first language and a practical choice for professional .NET work.

Short history

How a C# Program Is Structured

Console apps start in Main (or top-level statements in modern templates). Learn these parts once and reuse them everywhere.

Cheat sheet — first syntax

Your First C# Program — Hello World

Classic console style with an explicit Main method. Put this in Program.cs (or replace the template content).

using System;

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

Hello, World!

How It Works

1. Import System. using System; lets you write Console instead of System.Console.

2. Enter Main. .NET calls Main when the program starts.

3. Print. Console.WriteLine writes the string and a newline to the console.

How to Create and Run a Console App

Install the .NET SDK, then use the dotnet CLI. You do not need Visual Studio to get started.

dotnet new console -n HelloApp
cd HelloApp
dotnet run

Modern templates may use top-level statements (no explicit Main). The idea is the same: statements run from top to bottom when you call dotnet run.

Core Building Blocks

You do not need to master everything today. This map shows the main ideas you will meet as you continue with C#.

Where Is C# Used?

Common places you will see C# in the real world:

Key Takeaways