How to change a Window Owner using its handle

Question

I want to make a .NET Form as a TopMost Form for another external App (not .NET related, pure Win32) so it stays above that Win32App, but not the rest of the apps running.

I Have the handle of the Win32App (provided by the Win32App itself), and I've tried Win32 SetParent() function, via P/Invoke in C#, but then my .NET Form gets confined into the Win32App and that's not what I want.

Answer 1

I think you're looking for is to P/Invoke SetWindowLong( win32window, GWL_HWNDPARENT, formhandle );

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Answer 2

Yes! I've already have a P/Invoke import of SetWindowLongPtr (which is x64 safe). And using Reflector I searched upon the Form.Owner property ( i.e. the get_Owner(Form value) method ) and managed to change the owner with

SetWindowLongPtr(childHdl, -8, OwnerHdl)

I was looking what the -8 (0xFFFFFFFFFFFFFFF8) meant before I could post the solution here, but Joel has already pointed it out.

Thanks!