The Given Key Was Not Present in the Dictionary

When trying to add a local data cache to your Windows project and you are faced with the error "The given key was not present in the dictionary" or "The specified provider Microsoft.SqlServerCe.Client.3.5 does not exist"





It could be because you don't have SQL Express installed. I didn't have SQL Express installed because I am running the full version of SQL and didn't figure I needed it. Apparently, it is required because once I installed SQL Express the above problem was solved.