'AddressOf' expression cannot be converted to 'Long'

Question

I am getting this error with the following code ...

" 'AddressOf' expression cannot be converted to 'Long' because 'Long' is not a delegate type. "

I thought AddressOf returned a long value in vb6 but I found out it now returns a "delegate" type in VB10 ... I am new to VB 10 and can't seem to wrap my head around this new type. Can anyone help explain to me how I can to turn a "delegate" type to a long value to pass to the "user32" SetWindowLong funtion?

    Private Const GWL_WNDPROC = -4
    Private Const WM_GETMINMAXINFO = &H24

    Public lpPrevWndProc As Long
    Public gHW As Long

    Public Structure POINTAPI

        Dim x As Long
        Dim y As Long

    End Structure

    Public Structure MINMAXINFO

        Dim ptReserved As POINTAPI
        Dim ptMaxSize As POINTAPI
        Dim ptMaxPosition As POINTAPI
        Dim ptMinTrackSize As POINTAPI
        Dim ptMaxTrackSize As POINTAPI

    End Structure
 
    Private Declare Function SetWindowLong Lib "user32" Alias "SetWindowLongA" (ByVal hwnd As Long, ByVal nIndex As Long, ByVal dwNewLong As Long) As Long
    Private Declare Sub CopyMemoryToMinMaxInfo Lib "KERNEL32" Alias "RtlMoveMemory" (hpvDest As MINMAXINFO, ByVal hpvSource As Long, ByVal cbCopy As Long)
    Private Declare Sub CopyMemoryFromMinMaxInfo Lib "KERNEL32" Alias "RtlMoveMemory" (ByVal hpvDest As Long, hpvSource As MINMAXINFO, ByVal cbCopy As Long)
    Private Declare Function DefWindowProc Lib "user32" Alias "DefWindowProcA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long
    Private Declare Function CallWindowProc Lib "user32" Alias "CallWindowProcA" (ByVal lpPrevWndFunc As Long, ByVal hwnd As Long, ByVal Msg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long


    Public Sub Hook()

        lpPrevWndProc = SetWindowLong(gHW, GWL_WNDPROC, AddressOf WindowProc)

    End Sub

    Public Sub Unhook()

        Dim temp As Long
        temp = SetWindowLong(gHW, GWL_WNDPROC, lpPrevWndProc)

    End Sub

    Function WindowProc(ByVal hw As Long, ByVal uMsg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long

        Dim myScreens() As Screen = Screen.AllScreens
        Dim MinMax As MINMAXINFO
        If uMsg = WM_GETMINMAXINFO Then
            CopyMemoryToMinMaxInfo(MinMax, lParam, Len(MinMax))
            MinMax.ptMinTrackSize.x = 100
            MinMax.ptMinTrackSize.y = 100
            MinMax.ptMaxTrackSize.x = myScreens(0).Bounds.Height + 10
            MinMax.ptMaxTrackSize.y = myScreens(0).Bounds.Width + 10
            CopyMemoryFromMinMaxInfo(lParam, MinMax, Len(MinMax))
            WindowProc = DefWindowProc(hw, uMsg, wParam, lParam)
        Else
            WindowProc = CallWindowProc(lpPrevWndProc, hw, uMsg, wParam, lParam)
        End If

    End Function

Answer 1

Hi,

there's a forum about upgrading: http://social.msdn.microsoft.com/Forums/en-US/vbinterop/threads

Maybe a moderator can move it.

It would have helped if you had used the upgrade wizard so that at least some data types are matching. In general, if you want to translate, you should know both languages well before. Anyway, first step is changing Long to Integer. However, as VB6 didn't have a pointer type, Long was the replacment. In VB.Net, it is IntPtr now. So, wherever a pointer-size type is required, use IntPtr. Wherever a 32 bit size integer is required use Integer (or Int32).

I won't correct all API declarations now. Have a look at pInvoke.net and copy from there.

Regarding the question: SetWindowLong  has been superseded by SetWindowLongPtr. The last parameter is IntPtr now or a delegate:

Private Delegate Function WndProcDelegate(ByVal hWnd As IntPtr, ByVal msg As UInteger, ByVal wParam As IntPtr, ByVal lParam As IntPtr) As IntPtr

That means, keep two declarations of SetWindowLongPtr: One with IntPtr and one with WndProcDelegate as the last parameter's type.

Then you also need to change:

   Public lpPrevWndProc As IntPtr
   Public gHW As IntPtr

   Public Sub Hook()

      lpPrevWndProc = SetWindowLongPtr(gHW, GWL_WNDPROC, AddressOf WindowProc)

   End Sub

   Public Sub Unhook()

      Dim temp As IntPtr
      temp = SetWindowLongPtr(gHW, GWL_WNDPROC, lpPrevWndProc)

   End Sub

   Function WindowProc(ByVal hw As IntPtr, ByVal uMsg As UInteger, ByVal wParam As IntPtr, ByVal lParam As IntPtr) As IntPtr
     '''' .....
   End Function

Let me know if I forgot something.

---

Armin

Answer 2

Iiin addition:

• The Len() function is not appropriate for calculating the size of an unmanaged structure because it calculates the size of the object if written to a file. That's not necessarily equal. Call System.Runtime.InteropServices.Marshal.SizeOf instead. So the call would be:
  
      RtlMoveMemory(MinMax, lParam, New IntPtr(Marshal.SizeOf(MinMax)))
  
  
• However, RtlMoveMemory can be replaced by Marshal.PtrToStructure resp. StructureToPtr:
  
     MinMax = DirectCast(Marshal.PtrToStructure(lParam, GetType(MINMAXINFO)), MINMAXINFO)
     '...
     Marshal.StructureToPtr(MinMax, lParam, False)

---

Armin