/define (Visual Basic)
Defines conditional compiler constants.
The /define option has an effect similar to using a #Const preprocessor directive in your source file, except that constants defined with /define are public and apply to all files in the project.
You can use symbols created by this option with the #If...Then...#Else directive to compile source files conditionally.
/d is the short form of /define.
You can define multiple symbols with /define by using a comma to separate symbol definitions.
To set /define in the Visual Studio integrated development environment
Have a project selected in Solution Explorer. On the Project menu, click Properties. For more information, see Introduction to the Project Designer.
Click the Compile tab.
Modify the value in the Custom Constants box.