Concurrency exceptions in Entity Framework

Question

When calling SaveChanges / SaveChangesAsync in Entity Framework (CF, C#), if a change conflict occurs (for example, the values has been updated since last read thingy), then which of these two exceptions DbUpdateConcurrencyException OR OptimisticConcurrencyException shall I catch?

And what is the difference between them?

Answer 1

DbUpdateConcurrencyException is a specific exception thrown by DbContext, so this is the one to catch. This exception may be caused by an underlying OptimisticConcurrencyException, but if so, this exception is wrapped as the inner exception.

Not all update exceptions are caused by concurrency, so you also have to catch DbUpdateException after catching DbUpdateConcurrencyException (because the latter is a subtype of DbUpdateException).

See also Entity framework 5.0 handle optimistic concurrency exception?.

Answer 2

You will get an OptimisticConcurrencyException. Have a look at this.

Now coming to the diffrence.

• OptimisticConcurrencyException：thrown when an optimistic concurrency violation occurs（suppose more than one perople are changing to the same result，and this will cause the problem of not being sychronized)
• DbUpdateConcurrencyException：Exception thrown by DbContext when the expected behavior is that SaveChanges for an entity would result in a database update but in fact no rows in the database were affected. This shows that the database has been concurrently updated and a concurrency token that was expected to match did not actually match. State entries referenced by this exception are not serialized due to security and access to the state entries after serialization will return null.