private void ContractorList_PreviewMouseDoubleClick(object sender, MouseButtonEventArgs e)
 {
     NewContractor form = new NewContractor((Contractor)ContractorList.SelectedItem);
     form.Show();
     form.Closed += Form_Closed;
 }
 private void newContractorBtn_Click(object sender, RoutedEventArgs e)
 {
     NewContractor form = new NewContractor();
     form.Show();
     form.Closed += Form_Closed;
 }