Problem: Your project contains discontinued modules or assemblies
With Sitefinity upgrade certain assemblies or modules may be discontinued.
If you are upgrading to Sitefinity CMS 8.1 or higher, you should remove Telerik.Sitefinity.UI.Mvc.dll assembly and its references.
Solution
Telerik.Sitefinity.UI.Mvc.dll is removed and new assembly is introduced - Telerik.Sitefinity.Mvc.dll. Remove references to Telerik.Sitefinity.UI.Mvc.dll, if it is still referenced. Reference the new assembly Telerik.Sitefinity.Mvc.dll.
Other discontinued modules:
- Migration module is discontinued from Sitefinity 9.2.
- Sitefinity Thunder is discontinued from Sitefinity 11.0.