title: linq2sql: Cannot add an entity with a key that is already in use
body: <p>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: </p>
  
  <p>I also have a "global" datacontext that is used throughout the session.</p>
  
  <pre><code>    public static void Update(Enquiry enquiry)
      {
          OffertaDataContext db = new OffertaDataContext();
  
  
          db.Enquiries.Attach(enquiry);
          db.Refresh(RefreshMode.KeepCurrentValues, enquiry);
  
          db.SubmitChanges();
      }
  </code></pre>
  
  <p>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".</p>