In EF concurrency issue is resolved by using optimistic locking. Please refer ADO.NET chapter for what is optimistic locking and pessimistic locking?. To implement optimistic locking right click on the EDMX designer and set the concurrency mode to “Fixed” as shown in the below figure.
Now whenever we have concurrency issues you should get “OptimisticConcurrencyException” error as shown in the below figure. You can then put a try / catch to handle this situation.