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Lesson 2 of 60 10 minBeginner

Your first C# program

Install the tools, create a console app, and understand every line of “Hello, World!”.

Install the tools

Install Visual Studio Community (free) and tick the “.NET desktop development” workload. It includes the .NET SDK. Alternatively install the .NET SDK plus VS Code with the C# Dev Kit extension.
Open a terminal and run dotnet --version. If you see a number like 9.0.100, the SDK is installed.

Create and run a console app

A console app runs in a text window. It is the best way to learn because there is no UI to distract you. In a terminal:

Terminal

1dotnet new console -n HelloApp2cd HelloApp3dotnet run

Output

Hello, World!

In Visual Studio: Create a new project → Console App → Next, give it a name, then press F5 (run with debugger) or Ctrl+F5 (run without debugger).

Every line explained

Here is the classic, complete form of the program. Click each part to see what it does:

Interactive

Anatomy of a C# program

Click a line of code (or a button below) to see what that part means.

Program.cs

1using System;2 3namespace HelloApp4{5    class Program6    {7        static void Main(string[] args)8        {9            // Print a message to the console10            Console.WriteLine("Hello, World!");11        }12    }13}

static void Main

Main is the entry point: the first method that runs when your program starts. static means it runs without creating an object, void means it returns nothing, and string[] args receives any command-line arguments.

The short version: top-level statements

New projects (.NET 6+) generate a much shorter Program.cs. The compiler adds the namespace, class and Main method for you behind the scenes. Both versions do exactly the same thing.

Program.cs

1// Program.cs (top-level statements)2Console.WriteLine("Hello, World!");

Output

Hello, World!

Write vs WriteLine

Program.cs

1Console.Write("Hello, ");2Console.Write("Ravi");3Console.WriteLine("!");      // ends the line4Console.WriteLine("Next line");

Output

Hello, Ravi!
Next line

Rules C# is strict about

C# is case-sensitive: Console works, console does not.
Every statement ends with a semicolon ;.
Text (strings) goes in double quotes: "Hello".
Every { needs a matching }.

Comments

Comments.cs

1// A single-line comment2 3/* A comment that4   spans several lines */5 6/// <summary>XML documentation comment, shown in IntelliSense.</summary>

Quick check

Which method runs first when a classic C# program starts?

Quick check

What is wrong with console.WriteLine("Hi")?

Practice

Write a program that prints your name on the first line, your city on the second line, and “I am learning C#” on the third line.

Show the solution

Solution.cs

1Console.WriteLine("Raviselva");2Console.WriteLine("Salem");3Console.WriteLine("I am learning C#");

Output

Raviselva
Salem
I am learning C#

Remember

Create and run a console app with dotnet new console and dotnet run (or F5 in Visual Studio).
Main is the entry point; top-level statements are a shorter way to write it.
Console.WriteLine prints and starts a new line; Console.Write does not.
C# is case-sensitive, statements end with ;, blocks use { }.

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