Entity Framework: "Store update, insert, or delete statement affected an unexpected number of rows (0)." [closed]

Question

I am using Entity Framework to populate a grid control. Sometimes when I make updates I get the following error:

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 can't figure out how to reproduce this. But it might have something to do with how close together I make the updates. Has anyone seen this or does anyone know what the error message refers to?

Edit: Unfortunately I am no longer at liberty to reproduce the problem I was having here, because I stepped away from this project and don't remember if I eventually found a solution, if another developer fixed it, or if I worked around it. Therefore I cannot accept any answers.

Answer 1

I ran into this and it was caused by the entity's ID (key) field not being set. Thus when the context went to save the data, it could not find an ID = 0. Be sure to place a break point in your update statement and verify that the entity's ID has been set.

From Paul Bellora's comment

I had this exact issue, caused by forgetting to include the hidden ID input in the .cshtml edit page

Answer 2

That's a side-effect of a feature called optimistic concurrency.

Not 100% sure how to turn it on/off in Entity Framework but basically what it's telling you is that between when you grabbed the data out of the database and when you saved your changes someone else has changed the data (Which meant when you went to save it 0 rows actually got updated). In SQL terms, their update query's where clause contains the original value of every field in the row, and if 0 rows are affected it knows something's gone wrong.

The idea behind it is that you won't end up overwriting a change that your application didn't know has happened - it's basically a little safety measure thrown in by .NET on all your updates.

If it's consistent, odds are it's happening within your own logic (EG: You're actually updating the data yourself in another method in-between the select and the update), but it could be simply a race condition between two applications.