System.Diagnostics.Debug.WriteLine in production code

I should probably know this already, but I'm not sure and I don't see it documented.

I use System.Diagnostics.Debug.WriteLine quite often during the development process to be able to track changes to variables or exceptions as I'm debugging the code. This is meant to make development and understanding what's happening easier only during development. I normally either comment out the code or delete it when I go to production.

I'm wondering what happens if I forget to comment the code out. Say, for example, that during the development cycle, I'm tracking error information that may log a connection sting to the output window using Debug.Write Line. This is obviously OK while developing, but I'm wondering if when I go live, if there is a risk here. Can someone attach a debugger to my live executable and trap this output? Or is it something that only produces output in Visual Studio?

And what about when we switch from debug to release? Does this code get ignored by the compiler if we compile for release?

All the members in the Debug class are marked with ConditionalAttribute, so the call sites won't be compiled into a Release build.

System.Diagnostics.Debug method calls are only present when the "DEBUG" conditional compilation symbol is defined. By default, the "DEBUG" symbol is defined only for debug builds.

Compilers that support ConditionalAttribute ignore calls to these methods unless "DEBUG" is defined as a conditional compilation symbol.

Since the Debug methods all have the [Conditional("DEBUG")] attribute on them, if you switch from Debug to Release you will have not have to worry about it as the calls to those methods will be removed (along with the other optimizations of a Release build).

Debug information is only visible when you're running in Debug mode. In Release mode no Debug statements will be visible (you can use Trace instead of Debug if you want these statements to be visible in Release mode).

http://support.microsoft.com/kb/815788