Hello world

The code

using System;
namespace HelloWorld
{
    public class Hello
    {
        public static void Main(String[] args)
        {
	        Console.WriteLine("Hello, World!");
        }
    }
}

Output

Hello, World!

How it works

namespace HelloWorld

• A namespace is a way to organize code and avoid name conflicts.
• Essentially, it’s a container for classes and other types.
• Here, we define a namespace called HelloWorld to contain our program.

{}

• Curly braces {} are used to define the beginning and end of code blocks.
• In short, we put them after we define a namespace, class, function, if statement, or any other code structure.
• Everything inside of them is part of that structure. In this case, everything between the {} after namespace HelloWorld is part of that namespace.

public class Hello

• A class is a blueprint for creating objects.
• For now, just think of it as a way to group related code together.
• We define a class named Hello to hold our program’s Main method.

public static void Main(String[] args)

• Here, we define (create) a method named Main.
• A method is a block of code that performs a specific task. It’s essentially the same as a function, just that it belongs to a class.
• public means that this method can be accessed from outside the class.
• static means that this method belongs to the class itself, rather than to instances of the class. Basically, we can call it using Hello.Main() without having to create an object of type Hello first.
• void says that this method does not return any value.
• String[] args is a parameter that allows the program to accept command-line arguments. Here, args is an array of strings. We’ll get onto function parameters, strings and arrays later on.

What’s special about Main?

• The Main method is the entry point of a C# program.
• Basically, it’s the first thing that runs when you start the program.
• Every C# program must have a Main method to run.

Console.WriteLine("Hello, World!");

• This line of code prints the text “Hello, World!” to the console (the command line interface).
• Console is a built-in class in C# that contains methods for working with the console (terminal window).
• WriteLine is a method of the Console class that outputs text to the console, followed by a new line.
• The text to be printed is passed as an argument to the WriteLine method.
• The double quotes " around Hello, World! tell C# that it’s a string literal (text).
• The semicolon ; at the end of the line indicates the end of a statement. We need to put a semicolon at the end of every statement in C#.

I don’t understand…

• Don’t worry if you don’t fully understand the explanation of the code!
• We will cover all the concepts in detail in other pages.

The base for all examples

This hello world program is essentially the base for which all other examples in this tutorial build upon. Whenever you see code examples, you can assume that the code is inside the Main method of the Hello class in the HelloWorld namespace.

using System;
namespace HelloWorld
{
    public class Hello
    {
        public static void Main(String[] args)
        {
            // Any code examples go here unless
            // explicitly stated otherwise.
        }
    }
}

You are welcome to rename the class and namespace to whatever you like, as long as you keep the Main method as it is.

For example, if an example states this code:

int result = 5 + 3;
Console.WriteLine(result);

You can assume that the full code looks like this:

using System;
namespace HelloWorld
{
    public class Hello
    {
        public static void Main(String[] args)
        {
            int result = 5 + 3;
            Console.WriteLine(result);
        }
    }
}