private void btnAdd_Click(object sender, EventArgs e)
 {
     Client cl = new Client();
     ManageClientInfo form = new ManageClientInfo(cl);
     form.ShowDialog();
     if (form.DialogResult == DialogResult.OK)
     {
         try
         {
             cl.ApplyChange();
         }
         catch (Exception ex)
         {
             MessageBox.Show(ex.Message, "Не удалось сохранить данные.");
             cl = null;
         }
     }
     UpdateListClients();
 }