Alex Rivera | Logout

LINQ To SQL exception with Attach(): Cannot add an entity with a key that is already in use

Asked 2009-11-18T18:52:20.757
15

Consider this typical disconnected scenario:

  • load a Customer object from SQL Server using LINQ To SQL
  • user edits the entity, and the presentation tier sends back the entity modified.
  • the data layer, using L2S, must send the changes to SQL Server

Consider this LINQ To SQL query whose intention is to take a Customer entity.

Cust custOrig = db.Custs.SingleOrDefault(o => o.ID == c.ID); //get the original
db.Custs.Attach(c, custOrig); //we don't have a TimeStamp=True property
db.SubmitChanges();

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

alt text

Question

  • How can you avoid this exception?
  • What's the best strategy for updating an entity that does NOT have/want/need a timestamp property?

Sub-Optimal Workarounds

  • manually set each property in the updated customer to the orig customer.
  • spin up another DataContext
c# linq-to-sql concurrency datacontext
Edit
Report

1 Answer

-4

Instead of creating a new context you could do this:

public void Update(Customer customer)
{
    Customer oldCustomer= db.Custs.First(c => c.ID == customer.ID);  //retrieve unedited 
    oldCustomer = customer;  // set the old customer to the new customer.
    db.SubmitChanges();  //sumbit to database
}
answered 2012-07-17T13:06:15.383

Your Answer