C# Write your first program
To write your first C# program, you will follow a series of simple steps. C# is a high-level, object-oriented programming language, and its syntax is designed to be simple and readable.
Here's a step-by-step guide to help you write and run your first C# program using either the .NET CLI (Command Line Interface) or an IDE like Visual Studio or Visual Studio Code.
Option 1: Using .NET CLI (Command Line Interface)
The .NET CLI allows you to create and run C# projects directly from the terminal or command prompt.
Step 1: Install .NET SDK
- Before writing your first C# program, ensure that the .NET SDK is installed on your system. You can download it from the official Microsoft .NET website.
- After installation, verify it by running:
This should return the version number of your installed SDK.dotnet --version
Step 2: Create a New Console Application
Open a terminal or command prompt.
Navigate to a folder where you want to create your project, or create a new folder:
mkdir MyFirstApp cd MyFirstApp
Run the following command to create a new console application:
dotnet new console -n MyFirstApp
This will create a project named
MyFirstApp
. Navigate into this folder:cd MyFirstApp
Step 3: View the Default C# Code
Inside the project folder, open the Program.cs
file. It contains basic code that prints a message to the console. The content should look like this:
using System;
class Program
{
static void Main(string[] args)
{
Console.WriteLine("Hello, World!");
}
}
This code includes:
using System;
: A directive that allows access to classes in theSystem
namespace.class Program
: A class definition, where the program’s code resides.static void Main(string[] args)
: TheMain
method is the entry point of the application.Console.WriteLine("Hello, World!");
: A line of code that prints "Hello, World!" to the console.
Step 4: Run the Program
Now that your program is created, you can run it using:
dotnet run
You should see the output:
Hello, World!
Option 2: Using Visual Studio
Visual Studio is a feature-rich Integrated Development Environment (IDE) that simplifies C# development.
Step 1: Install Visual Studio
- Download and install Visual Studio from https://visualstudio.microsoft.com/.
- During installation, ensure you select the .NET desktop development workload to enable C# project creation.
Step 2: Create a New Console Project
- Open Visual Studio.
- On the start screen, click Create a new project.
- From the list of templates, select Console App.
- Choose a project name, location, and click Create.
Step 3: View the Default Code
Visual Studio will create a new project with a Program.cs
file containing the default code:
using System;
class Program
{
static void Main(string[] args)
{
Console.WriteLine("Hello, World!");
}
}
Step 4: Run the Program
To run the program, simply click the Start button (a green triangle icon) or press F5
. Visual Studio will compile and run the program, and you will see the output in the console window:
Hello, World!
Option 3: Using Visual Studio Code
Visual Studio Code is a lightweight code editor that can be configured to work with C#.
Step 1: Install Visual Studio Code
- Download and install Visual Studio Code from https://code.visualstudio.com/.
Step 2: Install C# Extension
- Open Visual Studio Code.
- In the Extensions view (
Ctrl+Shift+X
), search for the C# extension (by Microsoft) and install it. This extension provides IntelliSense, debugging, and project management features.
Step 3: Create a New Console Application
Open a terminal in VS Code (
Ctrl+
``).Run the following command to create a new console application:
dotnet new console -n MyFirstApp cd MyFirstApp
Open the folder in Visual Studio Code:
- Go to
File
->Open Folder
. - Select the
MyFirstApp
folder.
- Go to
Step 4: View and Modify Code
You will see the default Program.cs
file with the same "Hello, World!" code.
Step 5: Run the Program
You can run the program in the terminal using:
dotnet run
Alternatively, you can set up the debugger to run the program by pressing F5
.
Understanding the Basic C# Code
using System;
This line tells the compiler that you want to use classes from the System
namespace, which contains basic system functionalities like Console
.
class Program
This defines a class named Program
. In C#, all code is encapsulated in classes.
static void Main(string[] args)
- The
Main
method is the entry point of every C# application. It is where the program starts execution. static
means this method belongs to the class itself, not an instance of the class.void
means this method does not return any value.string[] args
is an array of strings that can store command-line arguments passed to the program.
Console.WriteLine("Hello, World!");
Console
is a class in theSystem
namespace used to perform input and output operations.WriteLine
is a method that prints text to the console and moves the cursor to the next line.
Modifying the Program
Let’s modify the program to ask for the user’s name and greet them.
Updated Code:
using System;
class Program
{
static void Main(string[] args)
{
Console.Write("Enter your name: ");
string name = Console.ReadLine();
Console.WriteLine($"Hello, {name}!");
}
}
Explanation:
Console.Write
: Prints a message without moving to the next line.Console.ReadLine
: Reads a line of text input from the user.$"Hello, {name}!"
: String interpolation to include thename
variable inside the string.
Output:
Enter your name: John
Hello, John!