将 SQL 查询转换为 LINQ - 不起作用

Question

我要转换的 SQL 查询是：

select p.PhoneNumber_Id, p.State, p.Created

from PhoneNumberServiceItems p

join PhoneNumbers on p.PhoneNumber_Id = PhoneNumbers.Id

inner join (

    select PhoneNumber_Id, max(Created) as MaxDate

    from PhoneNumberServiceItems

    group by PhoneNumber_Id

) tm on p.PhoneNumber_Id = tm.PhoneNumber_Id and p.Created = tm.MaxDate

where PhoneNumbers.NumberRangeId = {Id}

我最终得到的 LINQ 代码如下，但这不起作用：

 var res =

        from serviceItems in _db.PhoneNumberServiceItems

        join nums in _db.PhoneNumbers on serviceItems.PhoneNumber_Id equals nums.Id

        where nums.NumberRangeId == id

        join serviceGroup in (from ps in _db.PhoneNumberServiceItems

                      group ps by ps.PhoneNumber_Id into numGroup

                      //join tm in _db.PhoneNumbers on psg.FirstOrDefault().PhoneNumber_Id equals tm.Id

                      select new

                      {

                          NumId = numGroup.FirstOrDefault().PhoneNumber_Id,

                          MaxDate = numGroup.Max(i => i.Created)

                      }) on new { PNId = serviceItems.PhoneNumber_Id, serviceCreated = serviceItems.Created } equals new { PNId = serviceGroup.NumId, serviceCreated = serviceGroup.MaxDate }

        select new

        {

            State = serviceItems.State,

            NumId = serviceGroup.NumId,

            Created = serviceGroup.MaxDate

        };

我知道我的 LINQ 是错误的，但我无法指出我在做什么不同。任何帮助，将不胜感激。

编辑：这是从 LINQ 生成的已编译 SQL

SELECT 

[Extent1].[State] AS [State], 

[Project4].[C1] AS [C1], 

[Project4].[C2] AS [C2]

FROM   [dbo].[PhoneNumberServiceItems] AS [Extent1]

INNER JOIN [dbo].[PhoneNumbers] AS [Extent2] ON [Extent1].[PhoneNumber_Id] = [Extent2].[Id]

INNER JOIN  (SELECT 

    [Project3].[C1] AS [C1], 

    (SELECT 

        MAX([Extent5].[Created]) AS [A1]

        FROM [dbo].[PhoneNumberServiceItems] AS [Extent5]

        WHERE [Project3].[PhoneNumber_Id] = [Extent5].[PhoneNumber_Id]) AS [C2]

Answer 1

这与您的查询等效。var res = from s in PhoneNumberServiceItems          join p in PhoneNumbers on s.PhoneNumber_Id equals p.Id          join tm in ( from p1 in PhoneNumberServiceItems                        group p1 by p1.PhoneNumber_Id into p_g                        select new {PhoneNumber_Id = p_g.Key,MaxDate = p_g.Max(i=> i.Created)  }  )                    on new {Created = s.Created, PhoneNumber_Id = s.PhoneNumber_Id}                          equals new { Created = tm.MaxDate, PhoneNumber_Id = tm.PhoneNumber_Id}             where p.NumberRangeId == {Id}            select new                    {                        s.PhoneNumber_Id,                        s.State,                        s.Created                    };

Answer 2

尝试以下更简单的方法： var res = (from nums in _db.PhoneNumbers.Where(x => NumberRangeId == id)         join  serviceItems in _db.PhoneNumberServiceItems on nums.PhoneNumber_Id equals serviceItems.Id         select new {serviceItems = serviceItems, nums = nums})         .OrderByDescending(x => x.serviceItems.Created)         .GroupBy(x => x.nums.PhoneNumber_Id)         .Select(x => x.First())         .Select(x => new {Id = x.nums.PhoneNumber_Id, state = x.serviceItems.State,  maxDate = x.serviceItems.Created})         .ToList();

Answer 3

var recentPhoneNos=  from psi in _db.PhoneNumberServiceItems                     group psi by psi .PhoneNumber_Id into psiTemp                    select new {                       PhoneNumber_Id = psiTemp.Key,                       MaxDate = psiTemp.Max(i=> i.Created)                    };var res=from serviceItems in _db.PhoneNumberServiceItems        join nums in _db.PhoneNumbers on serviceItems.PhoneNumber_Id equals nums.Id        join serviceGroup in recentPhoneNos on nums.Id equals serviceGroup .PhoneNumber_Id         where nums.NumberRangeId == id && serviceGroup.MaxDate         select new {                    State = serviceItems.State,                    NumId = serviceGroup.NumId,                    Created = serviceGroup.MaxDate       } ;