Single-Line Comments

The simplest way to write a comment in C# is with two forward slashes: //. Everything on the same line after // is completely ignored by the compiler.

class Program
{
    static void Main()
    {
        // Prints a greeting
        Console.WriteLine("Hello!");
    }
}

A single-line comment does not have to sit on its own line. It can also appear directly after code on the same line — this is called an "inline comment."

Console.WriteLine("Hello!"); // prints "Hello!" to the screen

A single-line comment in C# begins with the characters ____.

With //, you can also temporarily "turn off" a line of code without deleting it. This is called "commenting out." C# then treats the line as if it were not there at all.

class Program
{
    static void Main()
    {
        Console.WriteLine("Line 1");
        // Console.WriteLine("Line 2");
        Console.WriteLine("Line 3");
    }
}

What does this program print?

Console.WriteLine("A");
// Console.WriteLine("B");
Console.WriteLine("C");

Important: // only comments out text up to the end of the current line. A line break automatically ends the comment — the next line is read as normal code again.

A // comment automatically also applies to the next line of code.