How to write multi-line comments in C#?

Multi-line comments in C# are comments that span more than one line. They are useful for adding detailed explanations, documenting code blocks, or temporarily disabling large sections of code during development.

Syntax

Multi-line comments in C# use the following syntax −

/* This is a multi-line comment
   that can span multiple lines
   All text between /* and */ is ignored */

The compiler ignores everything between /* and */, making it perfect for lengthy explanations or code documentation.

Basic Multi-line Comment Example

using System;

namespace Demo {
    class Program {
        static void Main(string[] args) {
            /* This is a multi-line comment
               explaining the purpose of this program.
               It demonstrates how multi-line comments work in C# */
            
            // Single line comment for comparison
            Console.WriteLine("Hello World");
        }
    }
}

The output of the above code is −

Hello World

Using Multi-line Comments for Code Documentation

using System;

class Calculator {
    /* 
     * This method calculates the area of a rectangle
     * Parameters: length and width (both double values)
     * Returns: area as a double value
     * Formula: area = length × width
     */
    public static double CalculateArea(double length, double width) {
        return length * width;
    }
    
    static void Main(string[] args) {
        double result = CalculateArea(5.0, 3.0);
        Console.WriteLine("Area of rectangle: " + result);
    }
}

The output of the above code is −

Area of rectangle: 15

Using Multi-line Comments to Disable Code

using System;

class Program {
    static void Main(string[] args) {
        Console.WriteLine("This line will execute");
        
        /*
        Console.WriteLine("This line is commented out");
        Console.WriteLine("This line is also commented out");
        int x = 10;
        Console.WriteLine("x = " + x);
        */
        
        Console.WriteLine("This line will also execute");
    }
}

The output of the above code is −

This line will execute
This line will also execute

Key Rules for Multi-line Comments

• Multi-line comments start with /* and end with */.

• Everything between these delimiters is ignored by the compiler.

• Multi-line comments cannot be nested ? you cannot put one multi-line comment inside another.

• They can span any number of lines and can appear anywhere in your code.

Comparison of Comment Types

Conclusion

Multi-line comments in C# use the /* */ syntax and are essential for documenting complex code sections or temporarily disabling code blocks. They provide a clean way to add detailed explanations that span multiple lines without cluttering your code with numerous single-line comment markers.