visual studio 2008 - C# Directive to indicate 32-bit or 64-bit build

Question

Is there some sort of C# directive to use when using a development machine (32-bit or 64-bit) that says something to the effect of:

if (32-bit Vista)
    // set a property to true
else if (64-bit Vista)
    // set a property to false

but I want to do this in Visual Studio as I have an application I'm working on that needs to be tested in 32/64 bit versions of Vista.

Is something like this possible?

Answer 1

Can you do it at runtime?

if (IntPtr.Size == 4)
  // 32 bit
else if (IntPtr.Size == 8)
  // 64 bit