Getting a window's coordinates

[Borkenstein]

I am trying to use GetWindowRect or GetWindowPlacement to find the coordinates of a window that I have the handle for, but every time I try to use GetWindowRect, I get this error:

An unhandled exception of type 'System.NullReferenceException' occurred in testapplication.exe

Additional information: Object reference not set to an instance of an object.

Here is the code I am using:

Dim r As New RECT
    GetWindowRect(hwnd, r)
    MsgBox(r.Left)

hwnd is the window handle, the API calls are all declared public in a module. Here is my converted RECT structure:

Public Structure RECT
        Dim Left As Integer
        Dim Top As Integer
        Dim Right As Integer
        Dim Bottom As Integer
    End Structure

Anyone see why it would give me a null exception error? I know for sure that the window handle is valid because I can use SetForegroundWindow on the same variable and it brings the application to the front of the screen.

Thanks for any help/ideas you can give.