Courses/C#/Introduction to C#

Introduction to C#

Lesson 1 • Beginner Track

What You'll Learn

Understand what C# is and why it's one of the most in-demand programming languages
Learn how C# fits into the .NET ecosystem (desktop, web, games, mobile)
Write and run your first C# program with Console.WriteLine()
Understand the anatomy of a C# program: using, class, Main, and statements
Use string interpolation to combine text and variables in output
Know the difference between Console.Write() and Console.WriteLine()

💡 Real-World Analogy

Think of C# as a universal remote control. Just like one remote can control your TV, sound system, and streaming box, C# can build desktop apps, websites, mobile apps, and games — all with the same language. The .NET framework is the signal receiver that makes everything work together. You learn one "remote" and control an entire ecosystem.

What is C# and .NET?

C# (pronounced "C Sharp") is a modern, object-oriented programming language created by Microsoft in 2000. It was designed by Anders Hejlsberg (who also created TypeScript and Delphi) to be powerful yet approachable — combining the performance of C++ with the productivity of languages like Java and Python.

C# runs on the .NET platform, which provides a massive standard library, a garbage collector for automatic memory management, and cross-platform support. With .NET 8+, your C# code runs on Windows, macOS, and Linux. Here's what you can build:

🎮 Games — Unity (the world's most popular game engine) uses C# exclusively
🌐 Web APIs & Websites — ASP.NET Core powers enterprise backends at Microsoft, Stack Overflow, and more
🖥️ Desktop Apps — Windows Forms, WPF, and .NET MAUI for cross-platform UIs
📱 Mobile Apps — .NET MAUI and Xamarin for iOS/Android from a single codebase
☁️ Cloud & Microservices — Azure Functions, gRPC services, and containerised APIs

C# is consistently ranked in the top 5 most in-demand programming languages, with average salaries ranging from £35,000–£75,000 (UK) and $60,000–$130,000 (US) depending on specialisation.

📊 C# Program Anatomy

Part	Code	What It Does
Using directive	using System;	Imports the System namespace so you can use Console
Class declaration	class Program {}	Every C# program lives inside a class
Main method	static void Main()	The entry point — where your program starts running
Statement	Console.WriteLine("...");	An instruction that does something — ends with ;
String interpolation	$"Hello {name}"	Embed variables inside strings with $ prefix

🖥️ Setting Up C#

You can practise C# right here in the browser, but to run C# on your own machine:

Option 1: Visual Studio (Recommended for Windows)

Download Visual Studio Community (free) from visualstudio.microsoft.com
Select the ".NET desktop development" workload during installation
Create a new "Console App" project and start coding

Option 2: VS Code + .NET SDK (All platforms)

Install the .NET SDK from dotnet.microsoft.com
Install VS Code with the C# extension
Run dotnet new console -n MyApp in terminal, then dotnet run

Option 3: Online (No install)

Use dotnetfiddle.net or the code editors in this course to practise instantly.

1. Your First C# Program

Every C# journey starts with "Hello, World!". Console.WriteLine() prints text to the console and moves to a new line. Try modifying the messages below:

Your First C# Program

Print messages to the console with Console.WriteLine().

Try it Yourself »

using System;

class Program
{
    static void Main()
    {
        Console.WriteLine("Hello, C# World!");
        Console.WriteLine("Welcome to C# programming!");
        Console.WriteLine("Let's build something amazing!");
    }
}

2. Console Output & String Interpolation

Console.Write() prints without a newline (the next output continues on the same line). String interpolation with $"" lets you embed variables directly inside strings — much cleaner than concatenation.

Console Output & Interpolation

Explore Write vs WriteLine and string interpolation.

Try it Yourself »

using System;

class Program
{
    static void Main()
    {
        // Writing output
        Console.WriteLine("=== Welcome to C# ===");
        Console.Write("This stays on ");
        Console.WriteLine("the same line.");

        // String interpolation
        string language = "C#";
        int year = 2024;
        Console.WriteLine($"Learning {language} in {year}!");

        // Escape characters
        Console.WriteLine("Line 1\nLine 2");
        Console.WriteLine("Tab\there");
        C
...

3. A Taste of Variables

Variables store data. C# is strongly typed — every variable has a specific type (string, int, double, bool). We'll cover types in depth in the next lesson, but here's a preview:

Variables Preview

See how different data types work in C#.

Try it Yourself »

using System;

class Program
{
    static void Main()
    {
        // Variables hold data
        string name = "Alice";
        int age = 25;
        double height = 1.68;
        bool isStudent = true;

        Console.WriteLine($"Name: {name}");
        Console.WriteLine($"Age: {age}");
        Console.WriteLine($"Height: {height}m");
        Console.WriteLine($"Student: {isStudent}");
    }
}

Pro Tips

💡 C# is case-sensitive: Console works, console doesn't. Watch your capitalisation.
💡 Every statement ends with a semicolon (;) — forgetting it is the most common beginner error.
💡 Use string interpolation ($"...") instead of concatenation ("Hello " + name). It's cleaner and easier to read.
💡 C# 9+ supports top-level statements: You can skip the class and Main method for simple programs. But learn the full structure first — you'll need it for real projects.

Common Mistakes

Missing semicolons — Every statement must end with ;. The compiler will give you a "CS1002: ; expected" error.
Wrong capitalisation — Console.Writeline won't work. It must be Console.WriteLine with a capital L.
Mismatched braces — Every { needs a matching }. Use an editor that highlights matching braces.
Forgetting "using System;" — Without this, the compiler doesn't know what Console is. You'll get a "CS0103: The name 'Console' does not exist" error.
Using single quotes for strings — In C#, strings use double quotes "hello". Single quotes 'h' are for individual characters (char type).

🎉 Lesson Complete

✅ C# is a modern, versatile language for games, web, desktop, and mobile
✅ .NET is the platform that runs C# code on Windows, macOS, and Linux
✅ Every program needs using System;, a class, and a Main method
✅ Console.WriteLine() prints with a newline; Console.Write() prints without
✅ String interpolation: $"Hello {name}" embeds variables in strings
✅ C# is strongly typed — every variable has a declared type
✅ Statements end with ; and code blocks use {} braces
✅ Next lesson: Variables & Data Types — the building blocks of every program

Introduction to C#

What You'll Learn

💡 Real-World Analogy

What is C# and .NET?

📊 C# Program Anatomy

🖥️ Setting Up C#

1. Your First C# Program

Your First C# Program

2. Console Output & String Interpolation

Console Output & Interpolation

3. A Taste of Variables

Variables Preview

Pro Tips

Common Mistakes

🎉 Lesson Complete

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