Entity Framework - The provider did not return a ProviderManifestToken string.

When I try to save data via GenericRepository using Entity Framework in Oracle 11g showing error. I tried lot and lot. But if i changed to normal method like conext.SaveChanges() it works.

"An error occurred while getting provider information from the database. This can be caused by Entity Framework using an incorrect connection string. Check the inner exceptions for details and ensure that the connection string is correct."

Inner Exception
"The provider did not return a ProviderManifestToken string."

Message
"An error occurred while getting provider information from the database. This can be caused by Entity Framework using an incorrect connection string. Check the inner exceptions for details and ensure that the connection string is correct."

In message it says problem in connection string, but in normal method it saved.

If anybody had met this issue and resolved, give me your ideas in ASAP please.