Linq - Sum()

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VS 2005:

Func<DataRow, decimal> filter = delegate(DataRow row)
                                                  {
                                                      if (row["dgvColumnItemId"].ToString() == itemId)
                                                          return (decimal)row["dgvColumnQty"];
                                                      return 0;
                                                  };

decimal totalQty = Enumerable.Sum<DataRow>(tripGlobal.curUserRows, filter);

decimal totalQty = Enumerable.Sum<DataRow>(tripGlobal.curUserRows, delegate(DataRow row)
                                                  {
                                                      if (row["dgvColumnItemId"].ToString() == itemId)
                                                          return (decimal)row["dgvColumnQty"];
                                                      return 0;
                                                  });

如果要查询DataTable.Rows的结果，视乎要把row放到一个list中.然后用list做TSource。

VS 2008:

decimal total = dataTable.AsEnumerable().Where(row => row["dgvColumnItemId"].ToString() == itemId).Sum(row => (decimal)row["dgvColumnQty"]);

decimal totalQty = (from DataRow row in dataTable.Rows
                               where row["dgvColumnItemId"].ToString() == itemId
                               select new
                               {
                                      qty = row["dgvColumnQty"]
                               }).Sum(a => Convert.ToDecimal(a.qty));