Question

在我的应用程序中，我想用数据库中符合特定条件的记录填充列表：

public ActionResult SelectYearGraph(int year)
{
    var lstAllSummaries = db.Summaries.ToList();

    var lstMonths =
       lstAllSummaries.Where(x => x.FlightDay.Year == year)
           .Select(x => x.TestDay.Month)
           .Distinct()
           .OrderBy(x => x)
           .ToList();

    List<string> lstMonthNames = new List<string>();
    List<int> lstCountSummaries = new List<int>();
    List<int> lstCountDailySummariesDifferentTime = new List<int>();

    var tsSix = new TimeSpan(6, 0, 0);
    var tsTen = new TimeSpan(22, 0, 0);

    foreach (var item in lstMonths)
    {
        var monthName = CultureInfo.CurrentCulture.DateTimeFormat.GetMonthName(item);
        lstMonthNames.Add(monthName);
        foreach (var item in lstMonths)
        {
            var monthName = CultureInfo.CurrentCulture.DateTimeFormat.GetMonthName(item);
            lstMonthNames.Add(monthName);
            lstCountDailySummaries.Add(lstAllSummaries.Count(x => x.FlightDay.Month == item && x.FlightDay.Year == year 
            && (x.FlightDay.TimeOfDay >= tsSix && x.FlightDay.TimeOfDay <= tsTen)
            && !x.deleted));
            lstCountDailySummariesDifferentTime.Add(lstAllSummaries.Count(x => x.FlightDay.Month == item && x.FlightDay.Year == year
            && (x.FlightDay.TimeOfDay > tsTen || x.FlightDay.TimeOfDay < tsSix)
            && !x.deleted));
        }
    }
    ... // more down here but not relevant to question
}

当我运行它时，我收到运行时错误：

LINQ to Entities不支持指定的类型成员'TimeOfDay'。仅支持初始值设定项，实体成员和实体导航属性。

我尝试了Date and Time Canonical Functions for LINQ-to-Entities，但收到了同样的错误。

如何在早上6点到晚上10点之间获取所有记录？

Answer 1

您不需要TimeOfDay只需阅读Hour Minute，Second DateTime即可在您的情况下获得相同的结果

TimeOfDay属性返回TimeSpan值，该值表示DateTime值的时间组件。

所以只需将您的代码更改为：

...
&& (DbFunctions.CreateTime(x.TestDay.Hour, x.TestDay.Minute,x.TestDay.Second) > DbFunctions.CreateTime(6,0,0) 
&& (DbFunctions.CreateTime(x.TestDay.Hour, x.TestDay.Minute, x.TestDay.Second) < DbFunctions.CreateTime(22,0,0))
...

寻找跨越午夜的时间的问题是，虽然时间可以是在早上6点之后和晚上10点之间，但是在晚上10点之后和早上6点之前也是如此。

您需要将AND更改为OR

...
&& (
  (DbFunctions.CreateTime(x.TestDay.Hour, x.TestDay.Minute,x.TestDay.Second) > DbFunctions.CreateTime(22,0,0) 
  || (DbFunctions.CreateTime(x.TestDay.Hour, x.TestDay.Minute, x.TestDay.Second) < DbFunctions.CreateTime(6,0,0))
)
...

Answer 2

var query = from x in db.Summaries
            let time = DbFunctions.CreateTime(x.TestDay.Hour, x.TestDay.Minute, x.TestDay.Second)
            where x.FlightDay.Year == year
                && !x.deleted
                && (time < DbFunctions.CreateTime(6, 0, 0))
                && (time > DbFunctions.CreateTime(22, 0, 0))
            group x by x.FlightDay.Month into summaries
            let month = summaries.Key
            select new
            {
                Month = month,
                Count = summaries.Count(),
                DifferentCount = (from d in db.DailySummaries
                                  let timed = DbFunctions.CreateTime(d.TestDay.Hour, d.TestDay.Minute, d.TestDay.Second)
                                  where d.FlightDay.Year == year && d.FlightDay.Month == month                    
                                        && !d.deleted
                                        && (timed < DbFunctions.CreateTime(6, 0, 0))
                                        && (timed > DbFunctions.CreateTime(22, 0, 0))
                                  select d).Count(),
            };

获取两次C＃Linq To Entities之间的记录列表

2 个答案: