I downloaded MS SQL Server 2014 Enterprise Edition from MSDN. I want to do a server backend in C# and MS SQL, but the problem is, whenever I want to do something with DB in
I'm guessing that your VS2013 isn't fully updated and that you need to update the database tooling component (SSDT) for SQL2014. I posted an answer on this a couple of days ago with some instructions.
Look at the Extensions and Updates in VS2013 and there should be an update available for SQL Server Data Tools.