How do I tell if my application is running as a 32 or 64 bit application?

Question

I'm trying to figure out how to tell if my application (compiled in VS2008 as Any CPU) is running as a 32 or 64 bit app.

Answer 1

I found this code from Martijn Boven that does the trick:

public static bool Is64BitMode() {
    return System.Runtime.InteropServices.Marshal.SizeOf(typeof(IntPtr)) == 8;
}

Answer 2

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

Answer 3

If you're using .Net 4.0, it's a one-liner for the current process:

Environment.Is64BitProcess

http://msdn.microsoft.com/en-us/library/system.environment.is64bitprocess.aspx