To elaborate,I was specifically getting an error upon Build of my web app: "The name 'RadPersistenceManager1' does not exist in the current context". The app doesn't complain until I do a Build. Then, I get the blue squiggly line under RadPersistenceManager1 in code-behind. In another thread, I found that if I 'View In Browser' the aspx page, I can circumvent the pre-build process. It then gives me another error: Unable to read storage content. Could not find file 'c:\...\visual studio 2013\Projects\...\App_Data\TelerikAspNetRadControlsPersistedState'.
Am I supposed to have something in the App_Data folder? If so, none of the Telerik doc mentions anything about it!