How does C# compiler remove Debug.Assert's in release builds?

Question

I was recently going through some code and considering whether I need to be careful with the expressions placed inside Debug.Assert statements, such as expensive op

Answer 1

I don't believe that Debug.Assert is special in any way; it's just using the Conditional attribute so that the compiler removes it when it detects that the 'preprocessor' define does not exist (C# does not have a preprocessor!).

You can use it like so to do the same thing (so long as you've defined DEBUG (or whatever symbol you want to switch on, TRACE is another popular one):

[Conditional("DEBUG"), Conditional("TRACE")]
public void DebugOnlyMethod() {
    Console.WriteLine("Won't see me unless DEBUG or TRACE is defined");
}