Linq to SQL - 左加入>比較

Question

我想在linq中執行一個左連接，它有一個date1> date2比較的sql，但無法弄清楚如何。這裏的SQL：

select 
rd.RouteDispatchID, 
    r.RouteNumber, 
    s.ShortDescription, 
    rd.DispatchDate, 
    rd.CreationDate, 
    e.FirstName, 
    e.LastName, 
count(md.MachineDispatchID) NumMachines, 
count(mdp.Pick) TotalPicks, 
sum(mh.BillsToStacker) + sum(mh.BoxCash) TotalCash, 
sum(mh.TubeCash) - sum(mh.CashOut) NetCoinsToTubes 
from dbo.RouteDispatch rd 
inner join dbo.Route r on rd.RouteID = r.RouteID 
inner join dbo.Reference s on rd.StatusCodeReferenceID = s.ReferenceID 
inner join dbo.Employee e on rd.CreatedByEmployeeID = e.EmployeeID 
left join dbo.MachineDispatch md on rd.RouteDispatchID = md.RouteDispatchID and md.IsSelected = 1 
left join dbo.MachineDispatchPick mdp on md.MachineDispatchID = mdp.MachineDispatchID 
**left join dbo.MachineHistory mh on md.MachineID = mh.MachineID and mh.ReadDate > m.LastServiceDate** 
group by rd.RouteDispatchID, 
    r.RouteNumber, 
    s.ShortDescription, 
    rd.DispatchDate, 
    rd.CreationDate, 
    e.FirstName, 
    e.LastName 

我把粗體問題的左連接。下面是我對LINQ到目前爲止，但我已經離開了mh.ReadDate> m.LastServiceDate，因爲我不知道如何做到這一點：

var query = from rd in db.RouteDispatches 
         join r in db.Routes on rd.RouteID equals r.RouteID 
         join s in db.References on new { StatusCodeReferenceID = rd.StatusCodeReferenceID } equals new { StatusCodeReferenceID = s.ReferenceID } 
         join e in db.Employees on new { CreatedByEmployeeID = rd.CreatedByEmployeeID } equals new { CreatedByEmployeeID = e.EmployeeID } 
         join md in db.MachineDispatches 
           on new { rd.RouteDispatchID, IsSelected = true } 
          equals new { md.RouteDispatchID, IsSelected = md.IsSelected.Value } into md_join 
         from md in md_join.DefaultIfEmpty() 
         join mdp in db.MachineDispatchPicks on md.MachineDispatchID equals mdp.MachineDispatchID into mdp_join 
         from mdp in mdp_join.DefaultIfEmpty() 
         join mh in db.MachineHistories on md.MachineID equals mh.MachineID into mh_join 
         from mh in mh_join.DefaultIfEmpty() 
         group new { rd, r, s, e, md, mdp, mh } by new 
         { 
          rd.RouteDispatchID, 
          r.RouteNumber, 
          s.ShortDescription, 
          rd.DispatchDate, 
          rd.CreationDate, 
          e.FirstName, 
          e.LastName 
         } into g 
         select new RouteView 
         { 
          RouteDispatchID = g.Key.RouteDispatchID, 
          RouteNumber = g.Key.RouteNumber, 
          Status = g.Key.ShortDescription, 
          DispatchDate = g.Key.DispatchDate.Value, 
          CreatedDate = g.Key.CreationDate.Value, 
          FirstName = g.Key.FirstName, 
          LastName = g.Key.LastName, 
          NumMachines = g.Count(), 
          TotalPicks = g.Count(), 
          TotalCash = (g.Sum(p => p.mh.BillsToStacker.Value) + g.Sum(p => p.mh.BoxCash.Value)), 
          NetCoinsToTubes = (g.Sum(p => p.mh.TubeCash.Value) - g.Sum(p => p.mh.CashOut.Value)) 
         }; 

任何人知道如何得到這個工作？

Answer 1

from rd in dc.RouteDispatches 
join r in dc.Routes on rd.RouteID equals r.RouteID 
join s in dc.References on rd.StatusCodeReferenceID equals s.ReferenceID 
join e in dc.Employees on rd.CreatedByEmployeeID equals e.EmployeeID 
from md in (
    from md in dc.MachineDispatches 
    where md.RouteDispatchID == rd.RouteDispatchID 
    && md.IsSelected == 1 
    select md 
).DefaultIfEmpty() 
from mdp in (
    from mdp in dc.MachineDispatchPicks 
    where mdp.MachineDispatchID == md.MachineDispatchID 
    select mdp 
).DefaultIfEmpty() 
from mh in (
    from mh in dc.MachineHistories 
    where mh.MachineID == md.MachineID 
    && mh.ReadDate > m.LastServiceDate 
    select mh 
).DefaultIfEmpty() 
group .... etc... 

Answer 2

我裝查詢起來Linqer，當我試圖把它轉換，我得到這個錯誤：

SQL cannot be converted to LINQ: Only "=" operator in JOIN expression can be used. ">" operator cannot be converted.

所以我感動的違規標準where子句。然後我能夠毫無問題地進行轉換。結果如下。

from rd in db.RouteDispatch 
join r in db.Route on rd.RouteID equals r.RouteID 
join s in db.Reference on new { StatusCodeReferenceID = rd.StatusCodeReferenceID } equals new { StatusCodeReferenceID = s.ReferenceID } 
join e in db.Employee on new { CreatedByEmployeeID = rd.CreatedByEmployeeID } equals new { CreatedByEmployeeID = e.EmployeeID } 
join md in db.MachineDispatch 
     on new { rd.RouteDispatchID, IsSelected = true } 
    equals new { md.RouteDispatchID, md.IsSelected } into md_join 
from md in md_join.DefaultIfEmpty() 
join mdp in db.MachineDispatchPick on new { MachineDispatchID = md.MachineDispatchID } equals new { MachineDispatchID = Convert.ToString(mdp.MachineDispatchID) } into mdp_join 
from mdp in mdp_join.DefaultIfEmpty() 
join mh in db.MachineHistory on md.MachineID equals mh.MachineID into mh_join 
from mh in mh_join.DefaultIfEmpty() 
group new {rd, r, s, e, mh} by new { 
    rd.RouteDispatchID, 
    r.RouteNumber, 
    s.ShortDescription, 
    rd.DispatchDate, 
    rd.CreationDate, 
    e.FirstName, 
    e.LastName 
} into g 
select new { 
    RouteDispatchID = (System.Int32?)g.Key.RouteDispatchID, 
    RouteNumber = (System.Int32?)g.Key.RouteNumber, 
    g.Key.ShortDescription, 
    DispatchDate = (System.DateTime?)g.Key.DispatchDate, 
    CreationDate = (System.DateTime?)g.Key.CreationDate, 
    g.Key.FirstName, 
    g.Key.LastName, 
    NumMachines = (Int64?)g.Count(), 
    TotalPicks = (Int64?)g.Count(), 
    TotalCash = (System.Int32?)(g.Sum(p => p.mh.BillsToStacker) + g.Sum(p => p.mh.BoxCash)), 
    NetCoinsToTubes = (System.Int32?)(g.Sum(p => p.mh.TubeCash) - g.Sum(p => p.mh.CashOut)) 
}