protected override void Tambah()
 {
     using (new StCursor(Cursors.WaitCursor, new TimeSpan(0, 0, 0, 0)))
     {
         var frm = new FrmEntryPenjualanProduk("Tambah Data " + this.Text, _bll);
         frm.Listener = this;
         frm.ShowDialog();
     }
 }
        protected override void Perbaiki()
        {
            var index = this.gridList.SelectedIndex;

            if (!base.IsSelectedItem(index, this.TabText))
            {
                return;
            }

            using (new StCursor(Cursors.WaitCursor, new TimeSpan(0, 0, 0, 0)))
            {
                var jual = _listOfJual[index];
                jual.tanggal_tempo_old = jual.tanggal_tempo;
                jual.item_jual         = _bll.GetItemJual(jual.jual_id).ToList();

                LogicalThreadContext.Properties["OldValue"] = jual.ToJson();

                var frm = new FrmEntryPenjualanProduk("Edit Data " + this.Text, jual, _bll);
                frm.Listener = this;
                frm.ShowDialog();
            }
        }