Question

I have a windows service that runs every 10 seconds … each time it runs, it takes some test data, modifies it and persists it to the database using the EntityFramework. However, on every second run, when I try to persist the change I get the following Optimistic Concurrency Exception:-

Store update, insert, or delete statement affected an unexpected number of rows (0). Entities may have been modified or deleted since entities were loaded. Refresh ObjectStateManager entries

I know for a fact that there is nothing else writing to that DB but my service which updates records every 10 seconds. What could be causing the concurrency exception here ?

I think a related entity somewhere in the object graph was getting modified prior to the second save operation.
All i am doing really is instantiating a new object context, and calling a save operation on some records i had retrieved using the same context.
The following code worked —

var ctx = new blahEntities();
var profile = ctx.ProfileSet.Where(pr=>pr.FirstName.Contains("a")).FirstOrDefault();
profile.Address = "modified";
ctx.SaveChanges();
ctx.Refresh(RefreshMode.StoreWins,profile);

Answer 1

The “unexpected number of rows (0)” indicates that more than likely you don’t have an ID field correctly mapped or defined in your entity model, or you are modifying a detached entity and attempting to save it and it doesn’t have key information.

Run SQL Server profiler, or Entity Framework Profiler, and see what is going on in the background.