Introduction to C# and .NET

Imagine you’re using your favorite mobile app, playing a game, or logging into a website. Behind every click, every animation, and every login screen, there’s code quietly working.

One of the languages powering those experiences is C#, a modern, fast, and widely used language created by Microsoft.

In this lesson, you'll meet C# for the first time , understand where it’s used, write your very first program, and even build a small welcome-message generator.

Today is the day you start thinking like a programmer.

Welcome Message Generator

Before we learn anything else, let’s imagine a tiny app. Every time it runs, it should display a friendly welcome message:

1
2
3
4
========================
   WELCOME TO C#
   Hello, Learner!
========================

You’ll write this program yourself by the end of this lesson.

What Is C# & Where Is It Used?

C# (pronounced “C Sharp”) is a modern programming language used all around the world.
Here’s where you can find it in action:

• 🎮 Games: Unity (the world’s most popular game engine) uses C#.
• 📱 Mobile Apps: using frameworks like Xamarin and .NET MAUI.
• 💻 Desktop Software: Windows applications, utilities, editors.
• 🌐 Web Applications: ASP.NET powers huge websites and APIs.
• 🤖 Automation & Robotics: used in tools, industrial systems, and bots.

If you learn C#, you can build almost anything, from mobile apps to video games to cloud software.

Setting Up Your Coding Environment

You have two simple options:

Option 1: DevsCall AI Online Code Runner

• No installation.
• No setup.
• Just open → write → run → get AI explanations.

This is the recommended way for beginners.

Option 2: VS Code (If You Want a Real IDE)

1. Install Visual Studio Code.
2. Install the C# extension.
3. Create a simple .cs file.
4. Run your program using the built-in terminal.

But remember: You can do this entire course directly inside DevsCall without installing anything.

Your First C# Program: Hello World

Here is the classic first program written in C#:

1
2
3
4
5
6
7
8
9
using System;

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

Run this in DevsCall or any C# environment, and you’ll see the message printed on screen.

How It Works

• using System;
  Gives you access to basic features like printing text.
• class Program
  Every C# program starts inside a class.
• static void Main()
  The starting point of your program, the first code that runs.
• Console.WriteLine()
  Prints text on the screen.

Once you understand this structure, you can write almost any program, calculators, games, mini-apps, anything.

Understanding Compilation & Execution

Before your program runs, something important happens behind the scenes:

• You write code → the C# compiler checks it.
• Compiler converts code into an intermediate language.
• The .NET runtime executes it on your device.

In simple words:
Your code → gets translated → into something the computer understands.

This translation is why C# is powerful, fast, and secure.

Let’s Build the “Welcome Message Generator”

Here is your first real project:

1
2
3
4
5
6
7
8
9
10
11
12
using System;

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

Run it, and your program will display a clean, formatted welcome screen.

Learn Together with AI

You don’t have to learn alone. Try these prompts in your AI Copilot:

• “Explain each line of a C# Hello World program.”
• “Rewrite the welcome message with different colors or ASCII art.”
• “Show a version that also prints my name.”
• “What else can I print using Console.WriteLine?”

AI will act like a friendly tutor who never gets tired of explaining.

Practice Time

Write a C# program that prints the following:

1
2
3
4
========================
   MY FIRST C# PROGRAM
   Welcome to DevsCall!
========================

Use Console.WriteLine() just like in the examples.

Example Solution

1
2
3
4
5
6
7
8
9
10
11
12
using System;

class Program
{
    static void Main()
    {
        Console.WriteLine("========================");
        Console.WriteLine("   MY FIRST C# PROGRAM");
        Console.WriteLine("   Welcome to DevsCall!");
        Console.WriteLine("========================");
    }
}

If your output matches, congratulations! You’ve officially written your first structured C# program.