Question

我有以下课程：

public class MyTrelloCard
{
    ...
    public DateTime? completed { get; set; }
    public Decimal? estHours { get; set; }
    public bool complete { get; set; }
}

...我想查询完成日期中每个日期的estHours数量。这些必须是可以为空的值，因为并非每张卡都已完成，并且并非每张卡都有估计的小时数。

目前我必须运行两个查询。第一个：

List<burnDownData> bData = (from c in cards
                            where c.complete
                            group c by new
                            {
                                date = Convert.ToDateTime(c.completed).Date
                            } into g
                            select new burnDownData
                            {
                                date = g.Key.date,
                                completedHours = g.Sum(x=>x.estHours) ?? 0
                            }).ToList();

返回已完成的所有卡片。

第二个用于迭代开始和结束时段之间的所有日期，并累计累计完成的小时数：

for (DateTime d = start; d.Date <= end; d = d.AddDays(1))
{
    if ((d.DayOfWeek >= DayOfWeek.Monday) && (d.DayOfWeek <= DayOfWeek.Friday))
    {
        List<C> values = new List<C>();

        Decimal xx = (from b in bData
                      where b.date.Date == d
                      select b.completedHours).SingleOrDefault();

        total = total + xx;

        values.Add(new C { v = d.ToString("d MMM") });
        values.Add(new C { v = total.ToString() });

        myRows.Add(new Row { c = values });
    }
}

但这似乎效率低下。有可能直接这样做吗？即取代循环的这一部分：

Decimal xx = (from b in bData
              where b.date.Date == d
              select b.completedHours).SingleOrDefault();

直接查询cards数据？

Answer 1

解释您的问题：

我想在完成的每个日期查询estHours的数量日期。这些必须是可以为空的值，因为并非每张卡都完成，并非每张卡都有估计的小时数加入

... as＆＃34;我试图获取每个completed日期实例的估计小时数之和，并希望允许空completed和{{1} }值＆＃34;。
您可以在Where子句中包含null检查：

estHours

例如：

var x = cards.Where(c => c.completed != null )
    .GroupBy(c => c.completed, (key, group) => new
    {
        dateComp = key.Value,
        totEstHrs = group.Sum(i => i.estHours)
    });
x.ToList().ForEach(
    item => Debug.Print("{0:MM/dd/yyyy} {1}", item.dateComp, item.totEstHrs));

产地：

04/28/2014 12

04/29/2014 3

修改要仅对日期部分进行分组（省略时间戳），您可以对ToShortDateString()值进行分组：

List<MyTrelloCard> cards = new List<MyTrelloCard>() { new MyTrelloCard() { completed = new DateTime(2014, 4, 28), estHours = 5, complete = true }, new MyTrelloCard() { completed = null, estHours = 5, complete = false }, new MyTrelloCard() { completed = null, estHours = null, complete = true }, new MyTrelloCard() { completed = new DateTime(2014, 4, 28), estHours = 7, complete = false }, new MyTrelloCard() { completed = new DateTime(2014, 4, 29), estHours = null, complete = false }, new MyTrelloCard() { completed = new DateTime(2014, 4, 29), estHours = 3, complete = false }, };

Answer 2

啊 - 所以你想要在你的范围内的每个工作日输入一个条目，即使那天没有数据。在这种情况下，建立一系列符合条件的日子，并分组加入您的卡片。

以下是：

var start = DateTime.Today;
var end = start.AddDays(14);

var cards = new[]{new {complete = true, completed = (DateTime?)DateTime.Now, estHours = new decimal?(3)} };

var days = Enumerable.Range(0, end.Subtract(start).Days)
.Select(x => start.AddDays(x))
.Where(x => !new []{DayOfWeek.Saturday,DayOfWeek.Sunday}.Contains(x.DayOfWeek));

var results = from d in days
              join c in cards on d equals c.completed.GetValueOrDefault().Date
              into cGrp
              select new {d, completedHours = cGrp.Sum(x => x.estHours)};

当然您不需要var cards =行，因为您已拥有自己的源代码！

修改 - 将一天的所有时间戳分组为1天。

我怎样才能做一次＆＃34;一次击中＆＃34;具有可空值的Linq查询？

2 个答案: