The specified cast from the materialized "System.Data.Objects.MaterializedDataRecord" type to "XXXX" is invalid.

An exception occurs when using Createqueryl in EF

This is the original problematic code.

Se. Createquery<departments> ("Select Departments.did, Departments.dname, Departments.dmanager from Departments")                            " "" "+ W.dmanager);});

Baidu Google can not find the answer online is really a mistake and then all the other sites to copy fraught

Post-Modification Code

  Se. Createquery<departments> ("Select Value T from departments as T")                            "   "" "+ W.dmanager);});

His method of body:
Public objectquery<t> createquery<t> (string querystring,params objectparameter[] parameters)

Reason: QueryString is esql instead of T-SQL

The specified cast from the materialized "System.Data.Objects.MaterializedDataRecord" type to "XXXX" is invalid.