C# Comments

Single-line comments

A single-line comment starts with two forward slashes (//). Everything after the slashes on that line is ignored by C#. You can put a comment on its own line or at the end of a line of code.

using System;

class Program
{
    static void Main()
    {
        // This line prints a greeting
        Console.WriteLine("Hello World!");
        Console.WriteLine("Learning comments"); // printed after the greeting
    }
}

Multi-line comments

When you need a comment that spans several lines, you can start it with /* and end it with */. Everything between those symbols is ignored, no matter how many lines it covers.

using System;

class Program
{
    static void Main()
    {
        /* This comment spans
           more than one line and
           explains the code below */
        Console.WriteLine("Comments are ignored by C#");
    }
}

Why use comments?

• To explain what a piece of code is meant to do.
• To leave reminders or notes for yourself and other developers.
• To temporarily disable a line of code without deleting it.
• To make complex programs easier to read and maintain.

A common trick is to comment out a line so it does not run, which is useful while testing. In the example below, the second message will not appear.

using System;

class Program
{
    static void Main()
    {
        Console.WriteLine("This line runs");
        // Console.WriteLine("This line is turned off");
    }
}