I believe that this is a kind of dependency issue, you can try the following:
1. Make sure that all referenced UI for WPF assemblies or of the same version (XAML or NoXaml, release version, .NET version of the ). 2. Make sure that the .NET version of the Telerik is the same as the Target Framework of the VS project. 3. You can remove all assemblies and add them again from the installation folder of the UI for WPF suite.
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