Sorry For bugs of my previous post
I was so tired....
It checks whether the DEBUG symbol exists in your code or not.
You can define these symbols using #define directive.
For best help I copy an exact bit of code from the book "professional C# 4 and .Net 4" :
// further on in the file
// do something
// some code that is only relevant to enterprise
// edition running on W2K
// do something else
// code for the leaner version
I do apologize again . . .