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;         }