We upgraded our NOXAML libraries to the latest S3 version (october 2019), from S2.
Since then, all telerik controls in the project give a similar error when the visual studio XAML designer is loaded...
'Control' not found in xmlns:telerik="http://schemas.telerik.com/2008/xaml/presentation"
'Control' an be any telerik Control type, like radcombobox or radgridview etc.
This occurs, where the control is defined inside the XAML like: <telerik:RadComboBox>...</telerik:RadComboBox>
as well as when we define a style like so...
<Style targettype="telerik:RadComboBox" BasedOn={StaticResource RadComboBoxStyle>..</Style>
As a solution we downgraded to the S3 version again because our project would produce over 300 of these errors, making the project difficult to manage.
As a note... The application does run like normal and the error disappear whilst Debugging.