Exception Details: System.Data.SqlClient.SqlException: Invalid object name ‘dbo.BaseCs’
This error means that EF is translating your LINQ into a sql statement that uses an object (most likely a table) named dbo.BaseCs, which does not exist in the database.
Check your database and verify whether that table exists, or that you should be using a different table name. Also, if you could post a link to the tutorial you are following, it would help to follow along with what you are doing.