Help us out a bit more... you've got a COM interop and a MFC client.... so where'd the .Net form come from?
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Error using .NET COM Interop on 64-bit OS
I have created a 32-bit VB.NET COM interop and a 32-bit MFC client app. I am running the MFC client app on a 64-bit OS. I have registered the COM interop using regasm.exe with /CodeBase. When I run my MFC app, I can successfully call simple functions from the COM that return strings and show msgboxes. However, I receive an error ( Object reference not set to an instance of an object ) from within the COM when it executes the following line:
Dim afrm As New MyForm
(where MyForm is a .NET windows form I created in the dll).
This error only occurs on a 64-bit OS. My MFC app works wonderfully on 32-bit OS. I have tried registering the .tlb using regtlb.exe instead of regasm.exe, but I couldn't call any functions after that. Please help! I have just started learning about COM Interops, and I really need some guidance with this one.
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Answers
Thanks for your comments. Just to update everyone, it turns out that I couldn't get the program running under my login to the 64-bit machine, but my boss can get it working under his login. So, it looks like a permissions problem. I really need to get this program running for everyone, not just my boss who would obviously have admin permissions, so I'm about to go into research mode again. Again, if someone has an idea of what I need to do, I would be very grateful for the help.
Hi, my apologies for not responding earlier. I was diverted from the project, and this is the first chance I've had to come back to it.
In response to your questions Lord Wabbit, MyForm is just a very simple VB.NET windows form that pops up a msgbox when clicked on, and moves two labels around on MouseMove. That is it. The form was created simply to show that I could integrate a VB.NET window into an MFC application via COM interop, whilst testing if the form still responds to mouse events. The form doesn't write to log files or access registries. The 64-bit machine that shows the error is running Windows Server 2003, while my development machine is 32-bit running windows XP.
However, I have been able to trace the bug down to the following line of code in MyForm.designer.vb:
Me.ClientSize = New System.Drawing.Size(252, 86)
Oddly enough, as soon as I removed this line of code, everything worked on both 32-bit and 64-bit machines, for all users. I really don't understand how removing this line of code could possibly fix the bug, but I think this shows that there is a problem with the form itself, and not with permissions or registrations as first thought. I will continue to dig deeper to see what exactly is going on here, and will post here if I have any more luck. Thanks again for your comments.
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by: LordWabbitPosted on 2009-07-31 at 05:08:58ID: 24988000
try changing the Platform to x86 under projct settings.