Thank you for writing.
This sounds like a multithreading issue.
The exception is shown when something in the layout is modified from a thread different than the painting one.
In the current implementation we lock the layout while painting to avoid glitches caused by animations or user code.
We intend to make our controls more thread-safe and user friendly in multithreading scenarios in the future.
However, this task is non-trivial and I cannot give you a timeframe when it will be done.
Meanwhile, you will have to avoid direct access of methods and properties from threads different than the main UI thread. In order to ensure the call is in the stack of the UI thread, you have to use Invoke()
There is a good article in the CodeProject
on the subject.
If you have further questions do not hesitate to write us.
All the best,
the Telerik team
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