Data Source Conflict

If you are developing BCS solutions in Visual Studio, you might have experienced the following error when you attempt to create or update a new item in an external list:

DataFormWebPartException: Data Source Conflict: Your changes conflict with those made concurrently by another user. Refresh the form and submit your changes again.

Solution: In your Visual Studio 2010 BCS project, find the Create or Update method that's failing. Verify that each of the fields in your input type descriptor have the Creator property (for the Create method) or Updater property (for the Update method) set to True.
Note, this property should not be set to true for the identifier field if the LOB auto generates the value. You also need to delete and re-add the external list before the changes take effect. (Because the object definition of the external content type is saved in the existing list and does not change when you update the BCS model.)