Linq使用小记之Group By

private void cmbStore_SelectedIndexChanged(object sender, EventArgs e)
        {
            DataTable vDt = ParamClass.ChargDt;
            var q = from b in vDt.AsEnumerable() group b by new { storeid = b["STOREID"], charg = b["charg"] } into g select new { g.Key.storeid, g.Key.charg };
            if (q != null && q.Count() > )
            {
                for (int i = ; i < gridPurchaseOrderDetail.Rows.Count; i++)
                {
                    (gridPurchaseOrderDetail.Rows[i].Cells["CHARG"] as DataGridViewComboBoxCell).DataSource = q.ToList();
                    (gridPurchaseOrderDetail.Rows[i].Cells["CHARG"] as DataGridViewComboBoxCell).ValueMember = "charg";
                    (gridPurchaseOrderDetail.Rows[i].Cells["CHARG"] as DataGridViewComboBoxCell).DisplayMember = "charg";
                    (gridPurchaseOrderDetail.Rows[i].Cells["CHARG"] as DataGridViewComboBoxCell).Value = q.ElementAt().charg;
                     getStockNum(i);
                }
            }
        }