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

Question

How do I tell if my application (compiled in Visual Studio 2008 as Any CPU) is running as a 32-bit or 64-bit application?

Answer 1

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

Environment.Is64BitProcess

Reference: Environment.Is64BitProcess Property (MSDN)

Answer 2

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