VB Forum / Win API / March 2008

Here is the deal:

I have got quite old application which was written in VB 6 using some
ActiveX Controls. My task is to perform some automatic test using Quick Test
Pro, which doesn't recognize those ActiveX controls, but it doesn't matter.

What I want to attain is to get control over an another application ActiveX
control using its window's (control's) handle.
http://rotanes.pl/Project1.exe <- here is really simple application
(requires VB 6 runtime) with a data grid (microsoft Data Grid Control 6.0,
MSDATAGRID.OCX) and one button, which changes data grid height. I want to be
able to do the same from, for example, .net application. Just pass the
handle (I can take it from any spy software) and perform the action.

What I discovered:

This ActiveX grid implements some COM interfaces, which are defined in the
same dll (ocx) file, just use OLE/COM Viewer and everything is visible. So I've
spent more then one week trying (using .net and C#) grab this interface
knowing only controls hwnd.

My attempts (I used to be a .net developer so I wrote everything in C#):

-> Implement interface _cGrid (which is the interface I would like to cast a
COM as) by myself:  [ComImport,
Guid("60E9A471-E4DF-4687-B419-15A644E8AD57]public interface _cGrid{.} Or use
the one generated by tlbimp.exe. -> import some extern procedures:
[DllImport("oleacc.dll", PreserveSig = false)]

[return: MarshalAs(UnmanagedType.Interface)]

public static extern object AccessibleObjectFromWindow(IntPtr hwnd, uint
dwId, ref Guid riid); (I tried this import in several different manners, for
example with UnmanagedType.IUnknonw, UnmanagedType.IDispatch, adding "out
IntPtr ppvd"as the last parameter and changing returned value to int.)
[DllImport("user32.dll")]

public static extern int SendMessage(int hWnd, uint Msg, int wParam, int
lParam); -> Dozens of tries to make everything working (unsuccessfully :( ):
_cGrid result = (_cGrid )InteropClass.AccessibleObjectFromWindow(handle, 0,
ref ITypeInfoGuid); <- throws en exception "Invalid Cast"
InteropClass.AccessibleObjectFromWindow(handle, 0, ref ITypeInfoGuid, out
_cGridPtr); <- after every statement execution _cGridPtr has different value
and it is different from Marshal.GetIUnknownForObject(obj) (I had reference
to the control for my learning purposes, but I won't have). It sends single
WM_GETOBJECT message to the control with 0xffffffff and 0x00000000
parameters (the second parameter referes to the second parameter of
AccessibleObjectFromWindow procedure) which always returns different value
(the subtraction of two sibling values equals 32, coincidence?)
Marshal.GetTypedObjectForIUnknown <- always throws "invalid cast exception"
or something like this. I would appreciate any (the simpler the better,
prefereably c# by can be managed/unmanaged c++ or VB as well) example of
code which works and can retrieve valid IUnknown pointer (or even cast
pointer as interface) from ActiveX control knowing only its hwnd. I found
followiong links helpful: [Some
basis]http://www.codeguru.com/csharp/csharp/cs_misc/com/article.php/c9065/http://www.c
larionmag.com/cmag/v1/v1n6callingole_part1.htmlhttp://www.codeproject.com/KB/COM
/COM_from_scratch_1.aspx
[I think the same
problem]http://www.vbforums.com/archive/index.php/t-158336.html [Hopeful
links]http://www.thescripts.com/forum/thread233284.htmlhttp://msdn2.microsoft.com/en-u
s/library/ms696137(VS.85).aspx
Especially -> Clients call this function to retrieve the address of an
object's IAccessible, IDispatch, IEnumVARIANT, IUnknown, or other supported
interface pointer. I originally posted this message on
http://www.codeguru.com/forum/showthread.php?p=1700068 Thanks in advance.