Multi-Line Comments

Sometimes a single line isn't enough to explain something. For longer notes, C# has a second notation: the multi-line comment. It begins with /* and ends with */ — everything in between is ignored, no matter how many lines it spans.

/* This is a
   multi-line comment
   that spans three lines. */
Console.WriteLine("Hello!");

Multi-line comments are especially well-suited for longer explanations — for example, describing at the top of a file what a program actually does.

/*
 * This program greets the user.
 * It is for practice purposes only.
 */
class Program
{
    static void Main()
    {
        Console.WriteLine("Hello!");
    }
}

A multi-line comment in C# begins with /* and ends with ____.

Another practical use: with /* */ you can "turn off" several lines of code at once, without having to add // in front of every single one.

class Program
{
    static void Main()
    {
        Console.WriteLine("Start");
        /*
        Console.WriteLine("Middle 1");
        Console.WriteLine("Middle 2");
        */
        Console.WriteLine("End");
    }
}

What does this program print?

class Program
{
    static void Main()
    {
        Console.WriteLine("Start");
        /*
        Console.WriteLine("Middle 1");
        Console.WriteLine("Middle 2");
        */
        Console.WriteLine("End");
    }
}

An important difference from //: a multi-line comment always has to be closed with */. If you forget it, the compiler treats all the following code up to the next */ as one giant comment — which can lead to very confusing errors.

A multi-line comment /* ... */ can span multiple lines.