Entity Framework 平均值，按查询分组

Question

我正在尝试将 SQL 查询转换为 ASP.NET MVC 5 控制器的 Linq。

SELECT TOP (10) 
    E.Surname, E.Name, E.Patronymic, AVG(CAST(IEEResult1 AS FLOAT))
FROM
    IEEResults AS I
JOIN
    Enrollee AS E ON E.Id = I.EnrolleeId
GROUP BY 
    I.EnrolleeId, E.Surname, E.Name, E.Patronymic
ORDER BY 
    AVG(CAST(IEEResult1 AS FLOAT)) DESC;

这就是答案。非常感谢afrazier！

 var result = db.IEEResults
    .Join(db.Enrollees, r => r.EnrolleeId, e => e.Id, (r, e) => new { e.Id, e.Surname, e.Name, e.Patronymic, r.IEEResult1 })
    .GroupBy(a => new { a.Id, a.Surname, a.Name, a.Patronymic })
    .Select(gr => new IEEResultsDTO
    {
        Id = gr.Key.Id,
        Surname = gr.Key.Surname,
        Name = gr.Key.Name,
        Patronymic = gr.Key.Patronymic,
        AvgResult = gr.Average(a => a.IEEResult1)
    })
    .OrderByDescending(b => b.AvgResult)
    .Take(10)
    .ToList().AsEnumerable();
            return View(result);

Answer 1

不要将 IEEResult1 放入您的组中，因为您要对这些项目的集合进行操作。我不太擅长查询语法，但这应该是 lambda 语法的有效查询。

var result = db.IEEResults
    .Join(db.Enrollees, r => r.EnrolleeId, e => e.Id, (r, e) => new { e.Id, e.Surname, e.Name, e.Patronymic, r.IEEResult1 })
    .GroupBy(a => new { a.Id, a.Surname, a.Name, a.Patronymic })
    .Select(gr => new {
        gr.Key.Id, gr.Key.Surname, gr.Key.Name, gr.Key.Patronymic,
        AvgResult => gr.Average(a => a.IEEResult1)
    })
    .OrderByDescending(b => b.AvgResult)
    .Take(10)
    .ToList();

Entity Framework 平均值，按查询分组

Entity Framework average, group by query

c#

sql

.net

linq

entity-framework-6