Clicking on a compressed C1.Win.Ribbon causes an error in RDP sessions

Clicking on a compressed C1.Win.Ribbon causes an error in RDP sessions

Posted by: stephan.pelz on 5 March 2026, 5:12 am EST

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  stephan.pelz

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  Posted 5 March 2026, 5:12 am EST

  Hello,

  we are using the C1.Win.Ribbon 8.0.20242.700 in our on premesis application. Recently some of our customers reached out to us with a problem regarding the ribbon. The problems looks like this:

  • the customer accesses the machine that runs the application via RDP
  • the C1.Win.Ribbon starts to collaps/compress some groups as it doesnt have enough space
    
    => as soon as the user clicks on one of the collapsed groups the users gets an error

  The error/stacktrace looks liks this:

  [code]TargetSite
  
  C1.Win.Accessibility.UiaItem get_d()

  Message
  
  Object reference not set to an instance of an object.

  Source
  
  C1.Win.Ribbon.8

  HResult
  
  -2147467261

  StackTrace
  
  at cm.a.get_d()
  
  at ch.a.WndProc(Message& a)
  
  at System.Windows.Forms.NativeWindow.Callback(HWND hWnd, MessageId msg, WPARAM wparam, LPARAM lparam)
  
  [/code]

  Additional info: The error does not occur at all RDP sessions, some target servers that run the application throw the error some do not. Our software version is the same on all target servers. So far we couldn’t find a difference between the RDP session.

  Did someone else in the community already face this error or does anyone know what we maybe have to change at the ribbon so we dont have this error. As the error message contains the hint for “C1.Win.Accessibility.UiaItem get” I assume we are missing some accessibility option here, tho a missing option shouldn’t cause an error.

  Best regards,
  
  Stephan

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  prabhat.sharma

  

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  Posted 6 March 2026, 3:27 am EST

  Hello Stephan,

  Thank you for reaching out to Mescius support.

  We have attempted to reproduce this behavior on our end using the same version of the controls, but so far, the Ribbon groups collapse and expand correctly without throwing any exceptions.

  To help us investigate this further, please run the attached sample RibbonRDPError.zip in one of the specific environments where the error occurs. If the error does not occur with this sample, please modify the attached project to more closely match your application’s setup, or provide a stripped-down version of your own project that reproduces the crash.

  Also, provide us with the specific details of that RDP machine, such as the Operating System version, display scaling (DPI) settings, RDP client version, and whether any third-party screen readers or accessibility tools are active on that specific machine.

  Once we have these details regarding the specific RDP environment, we can investigate this further and try to find a solution for you.

  If you have any other concerns, feel free to ask.

  Regards,
  
  Prabhat Sharma.

  RibbonRDPError.zip

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  stephan.pelz

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  Posted 13 March 2026, 6:01 am EST

  Hello,

  I am afraid i can’t reproduce the behaviour anymore. The server had some Windows updates and after those updates this bug does not appear anymore, neither in our software nor in the sample.

  I would close the topic for now and if the behaviour occurs in the future again i will come back to you with hopefully more information.

  Best regard,
  
  Stephan