#error lets you generate an error from a specific location in your code. For example:
#error Deprecated code in this method.
A common use of #error is in a conditional directive.
It is also possible to generate a user-defined warning with #warning (C# Reference).
// preprocessor_error.cs
// CS1029 expected
#define DEBUG
class MainClass
{
static void Main()
{
#if DEBUG
#error DEBUG is defined
#endif
}
}
Reference
C# Preprocessor Directives
Concepts
C# Programming Guide
Other Resources
C# Reference