Is it possible to create a Debug-only method in .NET?

Question

Is it possible to create a method which performs debugging assistance like the System.Diagnostics.Debug class?

I'm looking for a way to construct a method which when called by an assembly compiled with the DEBUG conditional compilation symbol defined, results in an operation, and which is a no-op when called by an assembly without the symbol defined.

If possible, I'd like it to be possible for the calls to the debugging methods to add minimal overhead or increase in size to the release version of the assembly.

To clarify, the debugging methods should be in an assembly compiled in Release mode. Calls to the methods should only generate operations when called from an assembly with the DEBUG symbol defined in the scope of the method call.

Answer 1

Add the Conditional attribute to the method, like this:

[Conditional("DEBUG")]
public void Whatever() {
    //...
}

Note that the method must return void, and cannot have any out parameters; otherwise, it would be impossible to remove a call to it.

The method will be compiled into the assembly, but CLS-compliant compilers will only emit calls to the method if the assemblies that they are compiling has DEBUG defined. Note that the C++ compiler is not CLS-compliant and will always emit the call.

Answer 2

ConditionalAttribute

BTW the code for the method being called remains in the assembly -- it's the calls to it that are removed at compilation time

Bonus topical blog post: http://blogs.msdn.com/ericlippert/archive/2009/09/10/what-s-the-difference-between-conditional-compilation-and-the-conditional-attribute.aspx

Answer 3

If you disassemble System.Diagnostics.Debug class using Reflector you can see that this is done using the [Conditional("DEBUG")] attribute:

public sealed class Debug
{
    private Debug();
    [Conditional("DEBUG")]
    public static void Assert(bool condition);
    // etc...
}