c# - 使用 LINQ 按小时分组

Question

我每 15 分钟将数据记录到 PowerStringHistorys 和 PowerCombinerHistorys 表中。我是 LINQ 的新手，正在尝试弄清楚如何创建一个查询，该查询按小时对我的数据进行分组，并为该小时平均电流。这是我目前所拥有的

        TimeZoneInfo easternZone = TimeZoneInfo.FindSystemTimeZoneById("Eastern Standard Time");
        DateTime UTC_StartingDate = TimeZoneInfo.ConvertTimeToUtc(StartingDate, easternZone);
        DateTime UTC_EndingDate = TimeZoneInfo.ConvertTimeToUtc(EndingDate, easternZone);

        var FirstQ = from p in db.PowerStringHistorys
                     join t in db.PowerStrings on p.string_id equals t.id
                     join u in db.PowerCombiners on t.combiner_id equals u.id
                     join s in db.PowerCombinerHistorys on p.recordTime equals s.recordTime
                     where p.recordTime >= UTC_StartingDate
                     where p.recordTime <= UTC_EndingDate
                     select new
                     {
                         Combiner = u.id,
                         Current = p.current,
                         RecordTime = p.recordTime,
                         Voltage = s.voltage
                     };

现在我需要按组合器和小时进行分组，这样我就可以对电流进行平均，并获得每个组合器在指定日期范围内每小时的千瓦时。

我需要以某种方式在查询中应用这个简单的公式:(平均瓦特每小时)/1000 = Kwh

所以我将以类似下面的内容结束。任何帮助将不胜感激。

Combiner 1     03/19/2012 1:0:0     1.85 Kwh
Combiner 1     03/19/2012 2:0:0     1.98 Kwh
Combiner 1     03/19/2012 3:0:0     2.05 Kwh
Combiner 1     03/19/2012 4:0:0     2.11 Kwh
Combiner 1     03/19/2012 5:0:0     2.01 Kwh
Combiner 1     03/19/2012 6:0:0     1.96 Kwh
Combiner 1     03/19/2012 7:0:0     1.85 Kwh
Combiner 2     03/19/2012 1:0:0     1.77 Kwh
Combiner 2     03/19/2012 2:0:0     1.96 Kwh
Combiner 2     03/19/2012 3:0:0     2.03 Kwh
Combiner 2     03/19/2012 4:0:0     2.11 Kwh
Combiner 2     03/19/2012 5:0:0     2.02 Kwh
Combiner 2     03/19/2012 6:0:0     1.98 Kwh
Combiner 2     03/19/2012 7:0:0     1.83 Kwh
Combiner 3     03/19/2012 1:0:0     1.77 Kwh
Combiner 3     03/19/2012 2:0:0     1.96 Kwh
Combiner 3     03/19/2012 3:0:0     2.03 Kwh
Combiner 3     03/19/2012 4:0:0     2.11 Kwh
Combiner 3     03/19/2012 5:0:0     2.02 Kwh
Combiner 3     03/19/2012 6:0:0     1.98 Kwh
Combiner 3     03/19/2012 7:0:0     1.83 Kwh

编辑

以上是我最初的问题。在处理了我收到的两个建议后，我得到了下面显示的代码。现在我只是将日期和总千瓦时返回到 View 中。我确实计划将 stringGroupedKwhlist 列表放入 HighChart 中供用户查看，并将 firstQ 查询结果放入 Telerik 网格中供用户过滤/排序/分组，以便他们可以处理详细信息。虽然代码确实有效并产生了我期望的结果，但我不确定它是否有效。因为我必须循环使用 foreach 我猜一旦它获得大量数据它可能会减慢速度。有没有更有效的方法来处理这个问题？

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web.Mvc;
using AESSmart.Models;

namespace AESSmart.Controllers
{
    public class StringKwh
    {
        public int CombinerID;
        public int StringID;
        public DateTime Interval;
        public Double KWH;

        public StringKwh(int combiner, int stringid, DateTime interval, double kwh)
        {
            CombinerID = combiner;
            StringID = stringid;
            Interval = interval;
            KWH = kwh;
        }
    }

    public class HomeController : Controller
    {
        private readonly AESSmartEntities db = new AESSmartEntities();

        public ActionResult Index()
        {
            //REPRESENTS DATE RANGE FOR A FULL DAY
            DateTime startingDate = new DateTime(DateTime.Now.Year, DateTime.Now.Month, DateTime.Now.Day, 0, 0, 1);
            DateTime endingDate = new DateTime(DateTime.Now.Year, DateTime.Now.Month, DateTime.Now.Day, 23, 59, 59);

            TimeZoneInfo easternZone = TimeZoneInfo.FindSystemTimeZoneById("Eastern Standard Time");
            DateTime utcStartingDate = TimeZoneInfo.ConvertTimeToUtc(startingDate, easternZone);
            DateTime utcEndingDate = TimeZoneInfo.ConvertTimeToUtc(endingDate, easternZone);

            var firstQ = from p in db.PowerStringHistorys 
                         from s in db.PowerCombinerHistorys
                         join t in db.PowerStrings on p.string_id equals t.id
                         join u in db.PowerCombiners on t.combiner_id equals u.id
                         where p.recordTime == s.recordTime
                         where p.recordTime >= utcStartingDate
                         where p.recordTime <= utcEndingDate
                         select new
                         {
                             Combiner = u.id,
                             StringId = p.string_id,
                             Current = p.current,
                             RecordTime = p.recordTime,
                             Voltage = s.voltage
                         };

            var groups = firstQ.ToList().GroupBy(q => new 
                                                { 
                                                    q.Combiner, 
                                                    q.StringId, 
                                                    Date = q.RecordTime.Date, 
                                                    Hour = q.RecordTime.Hour 
                                                });

            List<StringKwh> stringGroupedKwhlist = new List<StringKwh>();

            foreach (var group in groups)
            {
                stringGroupedKwhlist.Add(new StringKwh(
                                         group.Key.Combiner,
                                         group.Key.StringId,
                                         new DateTime(group.Key.Date.Year, group.Key.Date.Month, group.Key.Date.Day, group.Key.Hour, 0, 0),
                                         group.Average(g => g.Voltage * g.Current) / 1000d
                                         ));
            }

            var groupCombiner = stringGroupedKwhlist.GroupBy(q => new { q.CombinerID });
            double myTotalKwh = 0;

            foreach (var combinerGroup in groupCombiner)
            {
                myTotalKwh = Math.Round(combinerGroup.Sum(g => g.KWH), 3);
            }

            ViewBag.LifeTimeGeneration = myTotalKwh;
            ViewBag.myUTCStartDate = utcStartingDate;
            ViewBag.myUTCEndDate = utcEndingDate;

            return View();
        }

        public ActionResult About()
        {
            return View();
        }
    }
}

Answer 1

这可能会让你开始:

// Group by combiner ID, date, and hour
var groups = FirstQ.ToList()
    .GroupBy(q => new 
        { q.Combiner, Date = q.RecordTime.Date, Hour = q.RecordTime.Hour });

foreach (var group in groups)
{
    var combinerId = group.Key.Combiner;
    var interval = new DateTime(group.Key.Date.Year, group.Key.Date.Month, group.Key.Date.Day, group.Key.Hour, 0, 0);

    // power = voltage * current
    var kwh = group.Average(g => g.Voltage * g.Current) / 1000d;
}