从“日期时间”列中选择每天的“最小时间”值

mrwd 发表于 Dev

野蛮

有一个表（RecordDateTime列）：

 20.2.2021 12:54:34
 20.2.2021 13:54:34
 20.2.2021 14:54:34
 20.2.2021 15:54:34
 20.2.2021 16:54:34
 21.2.2021 11:50:00
 21.2.2021 13:54:34
 21.2.2021 14:54:34
 22.2.2021 10:00:00
 22.2.2021 13:54:34
 22.2.2021 14:54:34

我要去接

20.2.2021 12:54:34 
21.2.2021 11:50:00 
22.2.2021 10:00:00

并计算平均时间。

这是我当前的代码：

    public TimeSpan BeginTime(DateTime startDate, DateTime endDate)
    {
            var mainGridInfo = from w in db.LogModel
                               where w.RecordDateTime.Date >= startDate.Date && w.RecordDateTime.Date <= endDate.Date
                               group w by w.RecordDateTime.Date into test
                               select test.OrderByDescending(cs => cs.RecordDateTime.TimeOfDay).FirstOrDefault();

            var minDatesList = mainGridInfo.Select(s => s.RecordDateTime.TimeOfDay).ToList();

            double doubleAverageTicks = minDatesList.Average(timeSpan => timeSpan.Ticks);
            long longAverageTicks = Convert.ToInt64(doubleAverageTicks);

            return new TimeSpan(longAverageTicks);
    }

因此，据我了解，我将按日期分组进行测试，然后按DateTime列的时间部分进行排序，然后采用First或default（以消除可能的异常）。然后我将所有可用值选择到新列表中并计算这些值的平均值？为什么我的代码会产生异常？怎么了？

System.InvalidOperationException：'LINQ表达式'GroupByShaperExpression：KeySelector：rtrim（rtrim（strftime（'％Y-％m-％d％H：％M：％f'，a.RecordDateTime，'day of day'），' 0'），'。'），ElementSelector：EntityShaperExpression：EntityType：LogModel ValueBufferExpression：ProjectionBindingExpression：EmptyProjectionMember IsNullable：False
.OrderByDescending(cs => cs.RecordDateTime.TimeOfDay)' could not be translated. Either rewrite the query in a form that can be
翻译，或通过插入对“ AsEnumerable”，“ AsAsyncEnumerable”，“ ToList”或“ ToListAsync”的调用来显式切换到客户端评估。有关更多信息，请参见https://go.microsoft.com/fwlink/?linkid=2101038。

杰登

尝试以下操作：

            DataTable dt = new DataTable();
            dt.Columns.Add("Date", typeof(DateTime));

            dt.Rows.Add(new object[] {DateTime.ParseExact("20.2.2021 12:54:34", "dd.M.yyyy HH:mm:ss", System.Globalization.CultureInfo.InvariantCulture)});
            dt.Rows.Add(new object[] {DateTime.ParseExact("20.2.2021 13:54:34", "dd.M.yyyy HH:mm:ss", System.Globalization.CultureInfo.InvariantCulture)});
            dt.Rows.Add(new object[] {DateTime.ParseExact("20.2.2021 14:54:34", "dd.M.yyyy HH:mm:ss", System.Globalization.CultureInfo.InvariantCulture)});
            dt.Rows.Add(new object[] {DateTime.ParseExact("20.2.2021 15:54:34", "dd.M.yyyy HH:mm:ss", System.Globalization.CultureInfo.InvariantCulture)});
            dt.Rows.Add(new object[] {DateTime.ParseExact("20.2.2021 16:54:34", "dd.M.yyyy HH:mm:ss", System.Globalization.CultureInfo.InvariantCulture)});
            dt.Rows.Add(new object[] {DateTime.ParseExact("21.2.2021 11:50:00", "dd.M.yyyy HH:mm:ss", System.Globalization.CultureInfo.InvariantCulture)});
            dt.Rows.Add(new object[] {DateTime.ParseExact("21.2.2021 13:54:34", "dd.M.yyyy HH:mm:ss", System.Globalization.CultureInfo.InvariantCulture)});
            dt.Rows.Add(new object[] {DateTime.ParseExact("21.2.2021 14:54:34", "dd.M.yyyy HH:mm:ss", System.Globalization.CultureInfo.InvariantCulture)});
            dt.Rows.Add(new object[] {DateTime.ParseExact("22.2.2021 10:00:00", "dd.M.yyyy HH:mm:ss", System.Globalization.CultureInfo.InvariantCulture)});
            dt.Rows.Add(new object[] {DateTime.ParseExact("22.2.2021 13:54:34", "dd.M.yyyy HH:mm:ss", System.Globalization.CultureInfo.InvariantCulture)});
            dt.Rows.Add(new object[] { DateTime.ParseExact("22.2.2021 14:54:34", "dd.M.yyyy HH:mm:ss", System.Globalization.CultureInfo.InvariantCulture)});

            var days = dt.AsEnumerable().GroupBy(x => x.Field<DateTime>("Date").Date).ToList();
            DateTime[] minDate = days.Select(x => x.Min(y => y.Field<DateTime>("Date"))).ToArray();