Linq c外部加入＃

Question

如何执行正确的加入？我试图使用DefaultIfEmpty()函数，但没有效果。

有我的代码：

var AbsByDepartmentADM = (from abs in _dbContext.Absences 
           join e in _dbContext.DepartementProjects on abs.DepartementProjectID equals e.Id 

           into g 

           from c in g.DefaultIfEmpty() 
            where abs.Profil == "SHT" 

            group abs by new { abs.DepartementProject.Label } into z 
           select new 
           { 
            Matricule = z.Key.Label, 
            NumberOfAbsence = z.Count(), 
            WorkedHours = z.Sum(a => a.WorkedHours), 
            AbsencesHours = (8* z.Count() - z.Sum(a => a.WorkedHours)) 

           } into H 

           orderby H.NumberOfAbsence descending 
           select H); 

SQL查询生成：

{SELECT 
[Project1].[C3] AS [C1], 
[Project1].[Label] AS [Label], 
[Project1].[C1] AS [C2], 
[Project1].[C2] AS [C3], 
[Project1].[C4] AS [C4] 
FROM (SELECT 
    [GroupBy1].[A1] AS [C1], 
    [GroupBy1].[A2] AS [C2], 
1 AS [C3], 
CAST(8 * [GroupBy1].[A3] AS float) - [GroupBy1].[A4] AS [C4], 
[GroupBy1].[K1] AS [Label] 
FROM (SELECT 
    [Extent2].[Label] AS [K1], 
    COUNT(1) AS [A1], 
    SUM([Extent1].[WorkedHours]) AS [A2], 
    COUNT(1) AS [A3], 
    SUM([Extent1].[WorkedHours]) AS [A4] 
    FROM [dbo].[Absences] AS [Extent1] 
    INNER JOIN [dbo].[DepartementProjects] AS [Extent2] ON [Extent1].[DepartementProjectID] = [Extent2].[Id] 
    WHERE N'SHT' = [Extent1].[Profil] 
    GROUP BY [Extent2].[Label] 
) AS [GroupBy1] 
) AS [Project1] ORDER BY [Project1].[C1] DESC} 

SQL查询预计：

{SELECT 
[Project1].[C3] AS [C1], 
[Project1].[Label] AS [Label], 
[Project1].[C1] AS [C2], 
[Project1].[C2] AS [C3], 
[Project1].[C4] AS [C4] 
FROM (SELECT 
    [GroupBy1].[A1] AS [C1], 
    [GroupBy1].[A2] AS [C2], 
1 AS [C3], 
CAST(8 * [GroupBy1].[A3] AS float) - [GroupBy1].[A4] AS [C4], 
[GroupBy1].[K1] AS [Label] 
FROM (SELECT 
    [Extent2].[Label] AS [K1], 
    COUNT(1) AS [A1], 
    SUM([Extent1].[WorkedHours]) AS [A2], 
    COUNT(1) AS [A3], 
    SUM([Extent1].[WorkedHours]) AS [A4] 
    FROM [dbo].[Absences] AS [Extent1] 
    RIGHT JOIN [dbo].[DepartementProjects] AS [Extent2] ON [Extent1].[DepartementProjectID] = [Extent2].[Id] 
    WHERE N'SHT' = [Extent1].[Profil] 
    GROUP BY [Extent2].[Label] 
) AS [GroupBy1] 
) AS [Project1] ORDER BY [Project1].[C1] DESC} 

Answer 1

var AbsByDepartmentADM = from department in _dbContext.DepartementProjects 
           join abs in _dbContext.Absences on department.Id equals abs.DepartementProjectID into groupedResult 
           from groupedResultRight in groupedResult.DefaultIfEmpty() 
           group groupedResultRight by department.Label into grouped 
           let NumberOfAbsence = grouped.Count(t => t.DepartementProjectID != null) 
           let WorkedHours = grouped.Sum(a => a.WorkedHours != null ? a.WorkedHours : 0) 

           select new 
           { 
            DepartmentId = grouped.Key, 
            NumberOfAbsence, 
            WorkedHours, 
            AbsencesHours = (8 * NumberOfAbsence - WorkedHours) 
           }; 

Answer 2

的加入似乎并不起任何作用在你的LINQ代码中，所以我简化了一些特殊的用法。我用let做了DRY，但对于IQueryable可能效率不高，我不确定。

var AbsByDepartmentADM2 = from abs in _dbContext.Absences 
         where abs.Profil == "SHT" 
         group abs by abs.DepartementProject.Label into absg 
         let NumberOfAbsence = absg.Count() 
         let WorkedHours = absg.Sum(abs => abs.WorkedHours) 
         orderby NumberOfAbsence descending 
         select new { 
          Matricule = absg.Key, 
          NumberOfAbsence, 
          WorkedHours, 
          AbsencesHours = (8 * NumberOfAbsence - WorkedHours) 
         };