Question

Although this probably isn’t best practice, I am trying to clear a series of records from a database table, and then insert a series of records – some of which may have been in the original series, and others which may be new. I’m using linqtosql in C#. Pseudo-code I have to do this is below; it fails with “Cannot add an entity with a key that is already in use.”

using (dbDataContext context = new dbDataContext()
{
  // I've also tried using table.LinkedTable.Clear(); but that shows the same error
  while (table.LinkedTable.Count() > 0)
  {
    table.LinkedTable.RemoveAt(0);
  }

  foreach (ListItem item in SelectedItems.Items)
  {
    LinkedTable lt = new LinkedTable();
    lt.id = table.id;
    lt.SomeValue = item.SelectedValue;
    table.LinedTable.Add(lt);
  }
  context.SubmitChanges();
}

It seems like linqtosql is not taking note that I have removed items, before it tries to add items, causing a duplication error. Does anyone have any suggestions to correct this?

EDIT
If I add a SubmitChanges after doing the deletes, I then end up with this message.

“An attempt was made to remove a relationship between a table and a LinkedTable. However, one of the relationship’s foreign keys (LinkedTable.Id) cannot be set to null.”

Answer 1

You could try to use the ITable.DeleteAllOnSubmit method:

using (dbDataContext context = new dbDataContext()
{
  // table.LinkedTable is a EntitySet of LinkedTable objects,
  // we remove from the "LinkedTable" table, the records that
  // are related to the "table" object:
  context.LinkedTable.DeleteAllOnSubmit(table.LinkedTable);

  foreach (ListItem item in SelectedItems.Items)
  {
    LinkedTable lt = new LinkedTable();
    lt.id = table.id;
    lt.SomeValue = item.SelectedValue;
    table.LinedTable.Add(lt);
  }
  context.SubmitChanges();
}