When accessing database from WCF through Entity Framework, I got this error message:
This error is due to the primary key of the table is not specified as identity. In SQL Server, this is mandatory for primary key column.
To specify a primary as identity, right click on the table > Design > Click on primary key column. On the bottom, there is Column Properties. Scroll down to Identity Specification and expand it. The (Is Identity) should be set to Yes.
On different case, I also got “An error occurred while updating entries.”-request error. This is caused by the same problem: not specify the primary key as identity in SQL Server database.
Do remember that you do not need to refresh Entity Framework after specify the primary key as identity.