Conditional Compiling

#define 
#elif 
#else 
#endif 
#nullable 
#if 
#undef 
#region 
#endregion 
#error 
#warning 
#line 
#pragma 

VB.Net

#Const 
#ExternalSource 
#If Then 
#Else 
#Region 
#EndRegion 
#Disable 
#Enable