CODEWITHSUNDEEP
c#entity-framework
NuNn DaDdY
NuNn DaDdY

Reputation: 2992

Check to see if Entity has been Deleted

We're implementing Entity Framework inside a winforms application using DbContext/Code First and have the following question regarding the proper way to check/handle when an entity has been deleted/updated in another context.

For example, we have some auxiliary table data (e.g. StateCodes) and the user could go in another and add/remove states as needed. This auxiliary editor form utilizes it's own DbContext and saves the changes once the user exits the form. Upon returning to the main form, the main context is unaware of the changes made to the database so we'd like to reload the DbSet for the entity. Unfortunately, it appears that if we remove the "MI" state code it still exists in the Local property of the DbSet with an EntityState of unchanged even after we call "Load" to bring in everything.

Outside of completely disposing of the main context would the following be the best way to check and see if what entities have been removed from the database?

foreach (State state in db.States.Local)
{
    DbEntityEntry entry = db.Entry(state);
    DbPropertyValues databaseValues = entry.GetDatabaseValues();
    if (databaseValues == null)
    {
        db.States.Remove(state);
    }
    else
    {
        entry.OriginalValues.SetValues(databaseValues);
    }
}

Thank you for your help

Upvotes: 5

Views: 2762

Answers (2)

Noel
Noel

Reputation: 600

First, what Brad said. Only keep the context alive for the specific unit of work and dispose it. Not doing this will lead to nothing but headaches.

You can also check the entity's state by using the ObjectStateManager and pass in the object or entity key. You can also use the

public void Refresh( RefreshMode refreshMode, IEnumerable collection )

method off of the Context. Also, you can check the entry state.

http://msdn.microsoft.com/en-us/library/bb503718.aspx

Upvotes: 0

Brad Christie
Brad Christie

Reputation: 101604

You shouldn't keep the context live past its unit of work. The context should only survive as long as its needed, otherwise you're bound to run in to caching pitfalls like you're observing. (Also, the context really isn't that heavy where instantiating it when you need it is overly time-consuming/resource intensive).

If you really must keep it alive, you may want to look in to passing the context to the auxiliary form.

Mirrored from my comment, figured it's best served as an answer

Upvotes: 3

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