I would say the decisive error message is SqlException: Cannot insert explicit value for identity column in table 'Quest' when IDENTITY_INSERT is set to OFF.
A short search on google copy&pasting the message leads me to stackoverflow:
The answer with the most upvotes tells you to use the following SQL code.
Code:
SET IDENTITY_INSERT Table1 ON
INSERT INTO Table1
/*Note the column list is REQUIRED here, not optional*/
(OperationID,
OpDescription,
FilterID)
VALUES (20,
'Hierachy Update',
1)
SET IDENTITY_INSERT Table1 OFF