#error lets you generate an error from a specific location in your code.

#error text

where:

text

The text of the error that should appear in the compiler's output.

Remarks

A common use of #error is in a conditional directive. It is also possible to generate a user-defined warning with #warning.

Example

// preprocessor_error.cs
// CS1029 expected
#define DEBUG
public class MyClass 
{
   public static void Main() 
   {
      #if DEBUG
      #error DEBUG is defined
      #endif
   }
}

See Also

C# Preprocessor Directives