var result = (from DataRow dr in dt.Rows
                          join DataRow row in bgdl.Rows on dr["TDATETIME"] equals row["TDATETIME"] into a
                          from l in a.DefaultIfEmpty()
                          group l by new { TimePeriod = Convert.ToString(l["TDATETIME"]), Total = Convert.ToInt32(l["Total"]), BargainTo = Convert.ToDecimal(l["BargainTo"]) }
                              into b
                              orderby b.Key.TimePeriod ascending
                              select
                                  new
                                  {
                                      b.Key.TimePeriod,
                                      BargainTo = b.Sum(i => Convert.ToDecimal(i["BARGAINTO"])),
                                      b.Key.Total
                                  }).ToList();

dt 表结构  TDATETIME BARGAINTO
bgdl 表结构 TDATETIME Total
均为DataTable,通过 TDATETIME链接
对 dt 表的BARGAINTO 列 进行sum 计算

BargainTo = b.Sum(i => Convert.ToDecimal(i["BARGAINTO"])),[color=#FF0000] 该行报错 Column 'BargainTo' does not belong to table .[/color]
请教高手！
将两个table转换为 List<T>，就解决了；但还是想知道 用linq join两个datatable 统计怎么操作？是在没分了，抱歉啊