internal void AddHistory(HistoryItem item)
{
DB.HistoryItems.InsertOnSubmit(item);
DB.SubmitChanges();
_historyItems.Insert(0, item);
}
internal void DeleteHistory(HistoryItem item)
{
DB.HistoryItems.DeleteOnSubmit(item);
DB.SubmitChanges();
_historyItems.Remove(item);
}