Form closing when disconnect/reconnect from Remote Desktop when app contains a visible UltraToolbarsManager

Alex Kwong posted over 5 years ago

Dear all,

We recently replaced the traditional file menu by a UltraToolbarsManager control in our desktop application and everything works well -- except when we found out one issue that needs to be addressed.

When we use Remote Desktop and run our desktop application, Disconnecting the remote session and THEN reconnecting will cause the desktop application close. It happens when the reconnect happens ( we have code to check and confirmed the app is still running after disconnect ).

Some clues:

It happens when remote session RECONNECTS -- not when disconnect;
Only our desktop application closes -- all other apps within the remote session remains; so it should not be remote session timeout;
When UltraToolbarsManager is marked invisible ( visible = false ), it no longer close when reconnect;
When doing this via a Visual Studio debug, we found "System.Windows.Forms.Application.ThreadContext.RunMessageLoop() in Call Stack before System.Windows.Forms.Form.CheckCloseDialog() fires;
We tried to turn on Break on ALL EXCEPTIONS but nothing caught;
We put breakpoints on all codes we added on UltraToolbarsManager events but no luck;

Any idea how we can find out what is causing the issue? Thanks very much in advance.

-- Alex

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Offline Michael DiFilippo posted over 5 years ago in reply to Alex Kwong +1 verified
Hello Alex, Is the form closing or minimizing? When closing out a remote connection to a server operating system. The OS turns off the themes service...view reply »

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Offline Alex Kwong posted over 5 years ago in reply to Michael DiFilippo

Hi Michael,

Thank you very much for the valuable information. This is exactly what is happening ( i.e. Winform handle change ).

We are embedding a 3rd party exe within an infragistic Panel using window's SetParent() based on the win form's handle as one of the arguments. With the handle refresh after remote desktop reconnect, the embedded application terminates and leave the win form in an unknown state.

Is there anything that we can retain the win form handle? Or is there any reference from Microsoft that we can look for alternatives?

Thanks very much for your help.

-- Alex
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Verified Answer
Offline Michael DiFilippo posted over 5 years ago in reply to Alex Kwong

Hello Alex,

Is the form closing or minimizing?

When closing out a remote connection to a server operating system. The OS turns off the themes service. As such, our components are notified of the themes change. When it receives this notification, the UltraToolbarsManager (due to its use of the Desktop Window Manager to render aero glass) must force the host form to recreate it's window handle.

The duplication of the form caption and the windowstate change of child forms, is a bug in the framework; not our components. I've attached a sample (without our controls) that demonstrates this. Simply run the application and click the button; You will see the child form now has a Normal state, and the caption is duplicated.

Please adjust the sample to tailor to your application and see if it's the exact issue. Let me know if you have any questions.

5270.WindowsFormsApplication1.zip
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Offline Alex Kwong posted over 5 years ago

One more finding is that, if the main application is launched as mainform.ShowDialog(), it breaks. If it is launched via Application.Run( mainform ) then no crash happens.
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