public static DataTable UniteDataTableColumns(DataTable dt, String newColumnName, string ColumnName1, string ColumnName2)
        {
            //汇总的表达式
            string expression = "";                            
            expression = String.Format("{0}+'('+{1}+')'", ColumnName1, ColumnName2);          
            //增加汇总列
            System.Type myDataType = System.Type.GetType("System.String");
            DataColumn dcCol = new DataColumn(newColumnName, myDataType, expression, MappingType.Attribute);
            //增加合并列
            dt.Columns.Add(dcCol);
            return dt;
        }