Question

We use queries generated by Linq for data retrieval but for INSERT and UPDATE we do not allow generated SQL, but restrict to the use of stored procedures.

I connected the Update and the Insert behaviour in the DBML to the stored procedures.
The procedures are called, the data gets inserted/updated = all if fine, except in the case of optimistic concurrency.

If a record was changed between retrieval and update, the update should fail.

When Linq generates the Update statement itself, it throws a ChangeConflictException as expected, but using the stored procedure no Exception is thrown.

Thanks a lot for any help on this!

Answer 1

When configuring the UPDATE behavior to use the update stored procedure, Linq2SQL generates a method that is not throwing concurrency exceptions.
To handle optimistic concurrency I found a proposed solution in the MSDN forums

You can implement the Update method yourself in the patial DataContext class and throw a ChangeConflictException.

To achieve this you have to:

• write an Update stored procedure which takes the current and original values as parameters
  • using WHERE columnA = OriginalValueA ... to update only if the values were not changed
  • the last line in the stored procedure is RETURN @@ROWCOUNT
  • the rowcount lets you see if the row was updated or not
• in the DBML set the Update behaviour to “use runtime”
• the partial class xxxDataContext implement an Update method like this:
  • the code is taken from what Linq2SQL generates, just the last line to throw the exception is added

partial void UpdateYourEntityClass(YourEntityClass obj)
        {
            EntityClass original = ((YourEntityClass)(EntityClasss.GetOriginalEntityState(obj)));
            int result = this.YourEntityClassUpdate((...));
            if (result == 0) throw new ChangeConflictException();
        }

Working, but not straight forward.
Any other options?