linq2sql: Cannot add an entity with a key that is already in use

Question

I have a linq2sql setup where objects are sent from client side (flex via flourinefx) and attach them to a new datacontext a seen below:

I also have a "global" datacontext that is used throughout the session.

    public static void Update(Enquiry enquiry)
    {
        OffertaDataContext db = new OffertaDataContext();


        db.Enquiries.Attach(enquiry);
        db.Refresh(RefreshMode.KeepCurrentValues, enquiry);

        db.SubmitChanges();
    }

This approach usually works fine, but after a while I get the error "Cannot add an entity with a key that is already in use".

Answer 1

I was getting this error and it was because I had forgotten to set the Primary Key field in the database to "Identity Specification" (auto-increment). When I changed this I was good. Doh!

Answer 2

I think this error happens if you Attach an entity to a DataContext that was already loaded.

The code that causes the error is exactly like you show here? After creating the new OffertaDataContext do you query anything before the Attach?

Answer 3

This might not be your issue (I can't tell), but it was mine and as people google this it might help someone else. If you aren't using the built-in Linq-to-SQL designer or SQLMetal stuff to generate your Linq-to-SQL classes, or if you forgot to make your ID column an IDENTITY, you may be missing a property on your column attribute called "IsDbGenerated". Be sure your column attribute looks something like this:

<Column(Name:="ID", DbType:="Int NOT NULL IDENTITY", CanBeNull:=False, IsPrimaryKey:=True, IsDbGenerated:=True)>

Answer 4

In case you inserting several entities at once, may you are just trying to insert a duplicate entity into current datacontext. I know this is too simple, but it just happened to myself.