C# entity framework 总和时间跨度

Question

如何在 Entity Framework 中对列求和并绑定(bind)到标签中？

var result = (from t in db.aktivitaet
                          where t.idrapport == idrapport
                          group t by t.aktotal into d
                         select d).Sum();

            lblsum.Text = Convert.ToString(result.Sum( res => res));

像这样，但如果可能的话，我想像这样用 .toList() 来做:

var result = (from t in db.aktivitaet
                          where t.idrapport == idrapport
                         select new
                         {
                             t.aktotal
                         }).ToList();
            double sum = 0;
            foreach (var item in result)
            {
                sum += Convert.ToDouble(item.aktotal);
            }
            lblsum.Text = sum.ToString();

但是使用第二个代码块我得到了错误: Das Objekt des Typs\"System.TimeSpan\"kann nicht in Typ\"System.IConvertible\"umgewandelt werden。

Answer 1

var result = (from t in db.aktivitaet
                      where t.idrapport == idrapport
                     select new
                     {
                         t.aktotal
                     }).ToList();

var sum = result.Aggregate(TimeSpan.Zero, (total, next) => total.Add(next));

lblsum.Text = sum.ToString();

这应该可以解决问题