After I dragged and dropped an Ultra Panel in the form. It is showing:
Object of type 'Infragistics.Win.Appearance' cannot be converted to type 'Infragistics.Win.AppearanceBase'.
Need help how to resolve?
It sounds as though there are multiple versions of the Infragistics assemblies referenced by your project. If this is the case, the solution is to make sure that all of the Infragistics references are to the same version of the toolset. Often this is done by removing the references to the version that has less references.