Posted 28 October 2025, 1:40 am EST
Hello Andreas,
This error typically occurs because the WinForms designer is unable to properly serialize the IconSet property of the C1BitmapIcon.
Please try the following steps to resolve the issue:
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Make sure all ComponentOne assemblies (especially Ribbon and Framework) are from the same version and referenced from the official installation path (C:\Program Files (x86)\MESCIUS\ComponentOne\WinForms\bin\v4.x).
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Avoid mixing Ribbon assemblies such as C1.Win.Ribbon and C1.Win.C1Ribbon, as doing so can cause designer and version conflicts.
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If the issue persists, try uninstalling and reinstalling ComponentOne to repair any mismatched or corrupted assemblies.
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Test with a new WinForms project using the Ribbon control to determine if the issue is project-specific.
If the problem continues, please share a minimal sample that replicates the behavior, along with the version of ComponentOne used in your project and the version installed on your system.
If this information is sensitive, you can open a private support ticket here: https://developer.mescius.com/my-account/my-support/
You can also try to set the icon in code (e.g., in the form constructor) instead of through the designer.
Regards,
Uttkarsh.