How to emit compiler warnings and errors in C# .NET

In this post we saw how to use the “if” preprocessor in Visual Studio to “communicate” with the compiler. Here’s a reminder of the example code which we’ll re-use here:

private static void TryPreprocessors()
{
# if DEBUG
	Console.WriteLine("You are running the Debug build");
# elif RELEASE
	Console.WriteLine("You are running the Release build");
#else
	Console.WriteLine("This is some other build.");
# endif
}

In this post we’ll look at two more preprocessor types: warning and error. If you compile a project you can get one or more errors or warnings:

You can actively emit errors and warnings using the “warning” and “error” preprocessors. Here’s an example:

private static void TryPreprocessors()
{
# if DEBUG
	Console.WriteLine("You are running the Debug build");
# warning Don't deploy the Debug version!!!!
# elif RELEASE
	Console.WriteLine("You are running the Release build");
#error We're not ready for the deploy yet
#else
	Console.WriteLine("This is some other build.");
# endif
}

If I now select the Debug mode then I’ll see the warning:

…then if switch over to the Release build I get the exception:

View all various C# language feature related posts here.