Getting Started with C#

Learn how to set up your development environment and write your first C# program.

What You'll Learn

• Installing the .NET SDK
• Creating your first C# project
• Understanding the basic program structure
• Running and debugging C# code

What is C#?

C# is a modern, object-oriented programming language developed by Microsoft. It runs on the .NET platform and is used to build:

┌─────────────────────────────────────────────────────────┐
│                    C# Applications                       │
├──────────────┬──────────────┬──────────────┬───────────┤
│  Web Apps    │  Desktop     │   Mobile     │   Games   │
│  (ASP.NET)   │  (WPF/WinUI) │  (MAUI)      │  (Unity)  │
├──────────────┴──────────────┴──────────────┴───────────┤
│                     Cloud Services                       │
│              (Azure Functions, Microservices)            │
└─────────────────────────────────────────────────────────┘

Setting Up Your Environment

Step 1: Install .NET SDK

Download and install the .NET SDK from dotnet.microsoft.com.

Step 2: Verify Installation

dotnet --version

You should see a version number like 8.0.100 or higher.

Step 3: Install an IDE

Choose one of these options:

IDE	Best For
Visual Studio	Full-featured development
VS Code + C# Extension	Lightweight editing
JetBrains Rider	Cross-platform professional use

Your First C# Program

Create a New Project

# Create a new console application
dotnet new console -n HelloWorld

# Navigate to the project
cd HelloWorld

Understanding the Code

Open Program.cs:

// This is the simplest C# program
Console.WriteLine("Hello, World!");

In older versions or with explicit structure:

using System;

namespace HelloWorld
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Hello, World!");
        }
    }
}

Code Breakdown

┌─────────────────────────────────────────────────────────┐
│  using System;           // Import namespaces           │
├─────────────────────────────────────────────────────────┤
│  namespace HelloWorld    // Organize code               │
│  {                                                      │
│      class Program       // Container for code          │
│      {                                                  │
│          static void Main()  // Entry point             │
│          {                                              │
│              // Your code here                          │
│          }                                              │
│      }                                                  │
│  }                                                      │
└─────────────────────────────────────────────────────────┘

Running Your Program

# Run the application
dotnet run

Output:

Hello, World!

Basic Input and Output

Output to Console

// Simple output
Console.WriteLine("This prints a line");
Console.Write("This stays on the same line");

// String interpolation
string name = "Alice";
Console.WriteLine($"Hello, {name}!");

// Formatted output
int age = 25;
Console.WriteLine("Name: {0}, Age: {1}", name, age);

Reading Input

// Read a line of text
Console.Write("Enter your name: ");
string name = Console.ReadLine();

Console.WriteLine($"Hello, {name}!");

// Read a number
Console.Write("Enter your age: ");
int age = int.Parse(Console.ReadLine());

Console.WriteLine($"You are {age} years old");

Comments in C#

// This is a single-line comment

/* This is a
   multi-line comment */

/// <summary>
/// This is a documentation comment
/// Used by tools to generate documentation
/// </summary>

Complete Example

using System;

class Program
{
    static void Main()
    {
        // Welcome message
        Console.WriteLine("Welcome to C#!");
        Console.WriteLine("================");

        // Get user input
        Console.Write("What is your name? ");
        string name = Console.ReadLine();

        Console.Write("How old are you? ");
        string ageInput = Console.ReadLine();
        int age = int.Parse(ageInput);

        // Calculate birth year
        int birthYear = DateTime.Now.Year - age;

        // Display results
        Console.WriteLine();
        Console.WriteLine($"Hello, {name}!");
        Console.WriteLine($"You were born around {birthYear}");
        Console.WriteLine("Thanks for trying C#!");
    }
}

Project File Structure

After creating a project, you'll have:

HelloWorld/
├── HelloWorld.csproj    # Project configuration (XML)
├── Program.cs           # Your source code
├── obj/                 # Intermediate build files
└── bin/                 # Compiled output
    └── Debug/
        └── net8.0/
            └── HelloWorld.dll

The .csproj File

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net8.0</TargetFramework>
    <Nullable>enable</Nullable>
  </PropertyGroup>
</Project>

Common Commands

Command	Description
dotnet new console	Create console app
dotnet run	Build and run
dotnet build	Build only
dotnet clean	Clean build files
dotnet restore	Restore packages

Best Practices

Naming Conventions

• Classes: PascalCase (MyClass)
• Methods: PascalCase (DoSomething)
• Variables: camelCase (myVariable)
• Constants: PascalCase (MaxValue)

Common Mistakes

• Forgetting semicolons at the end of statements
• Case sensitivity: Console not console
• Not handling null input from Console.ReadLine()

Summary

You've learned how to:

• Install and set up the .NET SDK
• Create a new C# console project
• Write and run your first program
• Use basic input and output
• Understand the project structure

Next Steps

Ready to learn about variables and data types? Continue to Variables & Types!