Interop and Modal Forms

[clarkgriswald]

I have a .NET application that calls a method in a COM component to show a dialog. Unfortunately, you can't pass the .NET form to the COM component to set the owner form without a type mismatch:

_ComForm.Show vbModal, _DotNetForm

So, what that means is the form is displayed without a parent form. The problem is, if the user launches the COM form and then while the dialog is shown, clicks to another application and then returns to my application, the COM form is now behind the .NET owner form and most users won't know how to find that window. Is there any way around this?

[jmcilhinney]

Can you pass the Handle of the .NET form?

[clarkgriswald]

I would think so, yes.

[jmcilhinney]

Then that's what you should do. The Handle property of a Form is type IntPtr, which you can use as is if approriate or else call ToInt32 to get an Integer.

[clarkgriswald]

Ok, on the com side, how do I pass the handle to the .Show method?

[jmcilhinney]

No idea. Never done any COM development.

[manish.amq]

I'm also facing the same issue. Can you please help me , how you reslove the issue.

[Edgemeal]

Maybe use the SetWindowLong API to set the dialog's parent (owner) ?

Syntax is something like,...
SetWindowLong dialogForm.handle, GWL_HWNDPARENT, myForm.handle

[Niya]

Based on the description provided by the OP I would expect it to be done like this:-

_ComForm.Show vbModal, _DotNetForm.Handle.ToInt32

I'm assuming the COM method would take a 32 bit integer for the window handle assuming a 32 bit OS.

@Op

Could you provide the signature for that COM method ?

[manish.amq]

Im using VB6

Me.Show vbModal

oldOwner = SetOwner(Oconverstion.hWnd, Me.hWnd)

These are API im using to set the owner

Private Declare Function SetWindowLong& Lib "user32" Alias "SetWindowLongA" _
(ByVal hWnd As Long, ByVal nIndex As Long, ByVal dwNewLong As Long)
Const GWL_HWNDPARENT = (-8)

Public Function SetOwner(ByVal HwndtoUse, ByVal HwndofOwner) As Long
SetOwner = SetWindowLong(HwndtoUse, GWL_HWNDPARENT, HwndofOwner)
End Function

[Niya]

Im using VB6

Well you should make your own thread in the VB6 section. VB6 may have its own set of nuances.

[Joacim Andersson]

Using SetWindowLong with GWL_HWNDPARENT is the correct approach. However you should also use EnableWindow to disable the parent window and call it again to enable it when the modal form is closed.