private void DataGridview_DoubleClick(object sender, EventArgs e)
 {
     if (dangky == null || dangky.IsDisposed)
     {
         dangky = new PhieuDangKy(ctrl);
         dangky.Show();
     }
     else
     {
         dangky.Activate();
     }
 }
 private void bindingNavigatorAddNewItem_Click(object sender, EventArgs e)
 {
     if (dangky == null || dangky.IsDisposed)
     {
         dangky = new PhieuDangKy();
         dangky.Show();
     }
     else
     {
         dangky.Activate();
     }
 }