Unable to set FindWindow result to variable in .NET - variables

Question

I am attempting to use the FindWindow API using Visual Studio 2017 (.NET Framework 4.6.1) and VB.NET to retrieve the window handle for a currently running instance of Microsoft Word. I am finding that, although it has worked in the past (and is working in another area of the code) in one particular instance, although the FindWindow call is returning a value, I am not able to assign it to a variable. I have verified this in debug mode (screenshots available). I am trying to figure why the API call is not working in this particular instance.
Screenshots link: https://imgur.com/a/NuwpUyz
I have executed this call in some areas of the .NET code I am working with, so I know that it does work. I've changed the type in the definition of the "assignee" variable (from Object, to Integer, to IntPtr, etc., etc.) and rerun the application, with the same results (the "assignee" variable ends up with a value of zero, but the FindWindow call itself returns a integer value which appears to be the correct window handle.
The FindWindow API definition:
<DllImport("user32.dll")>
Public Shared Function FindWindow(ByVal strclassName As String, ByVal strWindowName As String) As Integer
End Function
The FindWindow API call:
.
.
.
Public hndMDIWord As Integer
.
.
.
.
If Word_Previously_Running Then
Try
_mdiWordApp = GetObject(, "Word.Application")
Catch ex As Exception
_mdiWordApp = New Word.Application
End Try
Else
_mdiWordApp = New Word.Application
End If
hndMDIWord = FindWindow("Opusapp", "")
If hndMDIWord <> 0 Then
SetParent(hndMDIWord, Me.Handle.ToInt32())
End If
I am expecting FindWindow to return an integer representing the window handle of the currently running instance of Word and than have that result assigned to the hndMDIWord variable. FindWindow does return the expected result, but the assignment statement for the hndMDIWord variable does not execute properly; hndMDIWord ends up with a value of zero. There is no error and no exception is thrown.
Any suggestions and/or insights will, of course, be greatly appreciated.
Regards,
Chris Fleetwood

Answer 1

I think the problem is: IntPtr is not compatible with Integer.
You need to declare return type as IntPtr:
<DllImport("user32.dll")>
Public Shared Function FindWindow(ByVal strclassName As String, ByVal strWindowName As String) As IntPtr
End Function
Because:
FindWindow has HWND return type
From MSDN handles are marshaled as IntPtr
Also there is a pinvoke.net website with examples of .net interop with wast majority of WinAPI functions.
Also hndMDIWord need to be declared as IntPtr and used accordingly, and other WinAPI functions need to be declared to use IntPtr for handlers too:
Public hndMDIWord As IntPtr
. . . .
If hndMDIWord <> IntPtr.Zero Then