An entity with the same identity already exists in this EntitySet

I'm trying to peform an update statement using WCF RIA Services, but everytime I update I keep getting "An entity with the same identity already exists in this EntitySet. Any insight on where I can start looking or figuring out what is wrong?

Step 1

LoadOperation<Analysis> AnalysisLP = ((App)Application.Current)._context.
                Load(((App)Application.Current)._context.GetAnalysisQuery().
                Where(o => o.ProjectID == Convert.ToInt32(((App)Application.Current).Project.Pro开发者_JS百科jectID)));

Step 2

 AnalysisLP.Completed += delegate
            {
                if (!AnalysisLP.HasError)
                {
                    Analysis = AnalysisLP.Entities.FirstOrDefault();
};

Step 3

         ((App)Application.Current)._context.Analysis.Attach(Analysis);
         ((App)Application.Current)._context.SubmitChanges(OnSubmitCompleted, null);

Can anyone help me, what is it i'm doing wrong?? thanks

Your object Analysis comes from the EntitySet via a query but is still attached to that EntitySet.

You just need to change its properties and call SubmitChanges. Do not try to attach it again.

To avoid the “An Entity with the same identity already exists in the EntitySet” exception, Entities that are updated, modified or deleted must always be fully refreshed from server upon saving, there can be no references held in memory to the previous instances of the entities. To prevent orhpaned instances from hanging around, I follow these rules:

Entity instances should not have any property changed event handlers assigned directly to them, rather use OnCreated or OnPropertyNameChanged partial methods instead.

When entities are added to an EntitySet, do not assign parent Entity instance references, use the foreign key ID property instead (myEntity.ParentalID = SelectedParent.ParentalID rather than myEntity.Parent = SelectedParent) because the SelectedParent probably isn’t getting reloaded upon saving because it isn’t part of the unit of work, so that reference will be held after the save and refresh.

Any combo boxes that are used as populate sources for Entity properties of the Entity need to have their EntitySet reloaded after saving as well; otherwise those related Entities populating the combo will hold references to the previous entity instance.