DataTable dt = new DataTable();var sum1 = dt.Compute("SUM(Volume)", "");DataRow[] drList = dt.Select("Name=‘AAA‘");var sum2 = drList.Sum(x => x.Field<decimal>("Volume"));var tJlbList = new List<TJlb_Mod>();var sum3 = tJlbList.Sum(o => o.FBcfs);var sum4 = tJlbList.SelectMany(x => x.TJlb_P_Items).Sum(o => o.FBcfs);