[c#] #ifdef in C#

I would like to do the below but in C# instead of C++

#ifdef _DEBUG
bool bypassCheck=TRUE_OR_FALSE;//i will decide depending on what i am debugging
#else
bool bypassCheck = false; //NEVER bypass it
#endif

#if DEBUG
bool bypassCheck=TRUE_OR_FALSE;//i will decide depending on what i am debugging
#else
bool bypassCheck = false; //NEVER bypass it
#endif

Make sure you have the checkbox to define DEBUG checked in your build properties.