DataGridViewComboBoxColumn grdCol = new DataGridViewComboBoxColumn();
   grdCol.DataSource = discountTbl;
   grdCol.DataPropertyName = "DiscountId";
   grdCol.DisplayMember = "DiscountName";
   grdCol.HeaderText = "Discount";
   grdCol.Name = "DiscountId";
   grdCol.ValueType = typeof(System.Int32);

   dgv.Columns.Add(grdCol);