I have a 10 year old ASP.Net MVC 3 application that was originally built using Telerik ASP.Net MVC 3. I am now trying to upgrade the website to MVC 5, and I believe I have the standard ASP.Net components upgraded, but I am really stuck with the Telerik components. If I try to run the MVC 5 application with the Telerik MVC 3 components, I get this TypeLoadException. I made an attempt to upgrade to Telerick MVC 5, but it seems like all of the classes have changed, and as you can imagine, an application that has been in active development for 10 years has a lot of code, and I do not think I can just go and re-write it all to use completely different types for the controls. What kind of upgrade path can you recommend to get this application to run on MVC 5? If there is a way to just overcome this TypeLoadException with the Telerik MVC 3 components or to upgrade to Telerik MVC 5 without having to rewrite the entire application, that would be great. Thank you.
System.TypeLoadException: Inheritance security rules violated by type: 'Telerik.Web.Mvc.PopulateSiteMapAttribute'. Derived types must either match the security accessibility of the base type or be less accessible.