Lambda GroupBy Sum

 DataTable dt = new DataTable();
 dt.AsEnumerable().GroupBy(r => r["ShopName"])
                         .Select(group => new { ShopName = group.Key, SumCount = group.Sum(item => Convert.ToInt32(item["SellCount"])) })

重点就是group.Sum(item => Convert.ToInt32(item["SellCount"]))这一句