给 DataTable 添加 列

 DataTable ta = b.CW_GZList(yue);
            ta.Columns.Add("sjgz", System.Type.GetType("System.Double"));
            foreach (DataRow dr in ta.Rows)
            {
                DataRow drEmployee = dr;
                drEmployee.BeginEdit();
                drEmployee["sjgz"] = Convert.ToDouble(drEmployee["yfgz"]) - Convert.ToDouble(drEmployee["koukuan"]);
                drEmployee.EndEdit();
            }

            RSDataList.DataSource = ta;  //b.CW_GZList(yue);
            RSDataList.DataBind();