title: c# linq discrad InsertOnSubmit
body: <p>i have a problem while using SubmitChanges() and InsertOnSubmit(),
  if the SubmitChanges fail and raise an exception the change set remains filled with the object that have a conflict in the db (e.g. the primary key already exists). the problem is that if i re-execute the piece of code that insert the element in the database   the SubmitChanges fail because the object with the wrong primary key is in the change set.
  The question is how to delete the first obj from the change set?</p>
  
  <pre><code>private void bInsInserisci_Click(object sender, RoutedEventArgs e)
      {
          Prodotto tmp = new Prodotto();
          try {
              tmp.idProdotto = InsProdCodProd.Text;
              tmp.tempo = Int32.Parse(InsProdTemp.Text);
              tmp.note = InsProdNote.Text;
              prodotti.InsertOnSubmit(tmp);
              db.SubmitChanges();
          }
          catch {
              System.Data.Linq.RefreshMode.KeepCurrentValues
          }
  
      }
  </code></pre>
  
  <p>Thanks </p>