c# - 另一个 LINQ Pivot 问题——将 SQL 脚本转换为 LINQ

Question

SO 上已经有一些关于 LINQ 枢轴的问题，虽然其中有几个问题概述了我的确切问题，但我无法成功地将它们转化为有效的解决方案。我觉得这主要是因为我的表中有联接。

因此，为了所有喜欢解决问题的 LINQ 爱好者的利益，这里有另一个难题供您解决。请通过将以下 SQL 存储过程脚本转换为 LINQ 来帮助我(并赢得一些声望点和我的尊重):

ALTER PROCEDURE [dbo].[GetTimesheetForWeekById]
    @timesheetid int,
    @begindate VarChar(20),
    @enddate VarChar(20)
AS
BEGIN

    SELECT T.TaskName,
        SUM(
            case DATEPART(weekday, TE.StartTime)
                WHEN 1 THEN DATEDIFF(minute, TE.StartTime, TE.EndTime) ELSE 0 END
            ) AS Sunday,
        SUM(
            case DATEPART(weekday, TE.StartTime)
                when 2 THEN DATEDIFF(minute, TE.StartTime, TE.EndTime) ELSE 0 END
            ) AS Monday,
        SUM(
            case DATEPART(weekday, TE.StartTime)
                when 3 THEN DATEDIFF(minute, TE.StartTime, TE.EndTime) ELSE 0 END
            ) AS Tuesday,
        SUM(
            case DATEPART(weekday, TE.StartTime)
                when 4 THEN DATEDIFF(minute, TE.StartTime, TE.EndTime) ELSE 0 END
            ) AS Wednesday,
        SUM(
            case DATEPART(weekday, TE.StartTime)
                when 5 THEN DATEDIFF(minute, TE.StartTime, TE.EndTime) ELSE 0 END
            ) AS Thursday,
        SUM(
            case DATEPART(weekday, TE.StartTime)
                when 6 THEN DATEDIFF(minute, TE.StartTime, TE.EndTime) ELSE 0 END
            ) AS Friday,
        SUM(
            case DATEPART(weekday, TE.StartTime)
                when 6 THEN DATEDIFF(minute, TE.StartTime, TE.EndTime) ELSE 0 END
            ) AS Saturday

    FROM Tasks T
    INNER JOIN TimeEntries TE on T.TaskID = TE.TaskID
    WHERE TE.StartTime BETWEEN 
        (CONVERT(datetime, @begindate, 103)) AND (CONVERT(datetime, @enddate, 103))
    AND TE.TimesheetID = @timesheetid
    GROUP BY T.TaskName
END

Answer 1

好吧，假设外键有一个对象表示，类似于:

        int timesheetId = ...
        DateTime start = ..., end = ...
        var qry = from timeEntry in ctx.TimeEntries
              let date = timeEntry.StartTime.Date
              where timeEntry.TimesheetId == timesheetId
                && date >= start
                && date <= end
              group timeEntry by timeEntry.Task.TaskName into grp
              select new {
                  TaskName = grp.Key,
                  Monday = grp.Where(x => x.StartTime.DayOfWeek == DayOfWeek.Monday).Count(),
                  Tuesday = grp.Where(x => x.StartTime.DayOfWeek == DayOfWeek.Tuesday).Count(),
                  Wednesday = grp.Where(x => x.StartTime.DayOfWeek == DayOfWeek.Wednesday).Count(),
                  Thursday = grp.Where(x => x.StartTime.DayOfWeek == DayOfWeek.Thursday).Count(),
                  Friday = grp.Where(x => x.StartTime.DayOfWeek == DayOfWeek.Friday).Count()
              };

不幸的是，一些细节取决于 SQL 提供程序 - 即哪些函数(如 DayOfWeek 等)可以成功映射为 TSQL。如果您遇到问题，请告诉我...