c# dataTable 合並兩個列到一個新列中

 public static DataTable UniteDataTableColumns(DataTable dt, String newColumnName, string ColumnName1, string ColumnName2)
        {
            //匯總的表達式
            string expression = "";                             
            expression = String.Format("{0}+'('+{1}+')'", ColumnName1, ColumnName2);           
            //增加匯總列
            System.Type myDataType = System.Type.GetType("System.String");
            DataColumn dcCol = new DataColumn(newColumnName, myDataType, expression, MappingType.Attribute);
            //增加合並列
            dt.Columns.Add(dcCol);
            return dt;
        }