Linq左外連接跨多個表檢索每個表的信息

Question

我是新來的linq，並希望執行跨三個表的連接。在SQL相當於什麼，我試圖做的是：

SELECT PM.Id, PM.new_clientId, ..... 
C.new_firstname, c.new_surname,..... 
A.new_addressid, A.new_addressline1, A.new_addressline2..... 
CY.new_county 

FROM partialMatch PM 
INNER JOIN new_client C ON PM.new_clientId = C.new_clientId 
LEFT OUTER JOIN new_address A ON C.new_addressId = A.new_addressId 
LEFT OUTER JOIN new_county CY ON A.new_countyId = CY.new_countyId 

WHERE PM.ownerId = @UserId AND PM.new_reviewed <> true 

我已經開發了LINQ的代碼是這樣的，但這些似乎並沒有被外連接，因爲它沒有返回任何結果，除非我註釋掉加入到地址和縣級表

var partialMatches = from pm in ContextService.CreateQuery<new_partialmatch>() 
          join c in ContextService.CreateQuery<new_client>()  on pm.new_ClientId.Id equals c.new_clientId 
          join a in ContextService.CreateQuery<new_address>() on c.new_AddressID.Id equals a.new_addressId 
          join cy in ContextService.CreateQuery<new_county>() on a.new_CountyID.Id equals cy.new_countyId 
          where pm.OwnerId.Id == _currentUserId && pm.new_Reviewed != true 

          select new 
          { 
           Id = pm.Id, 
           new_ClientID = pm.new_ClientId, 
           new_MatchingCRMClientID = pm.new_MatchingCRMClientId, 
           new_MatchingVulcanClientID = pm.new_MatchingVulcanClientID, 
           new_name = pm.new_name, 
           firstname = c.new_FirstName, 
           surname = c.new_Surname, 
           dob = c.new_DateOfBirth, 
           addressId = a.new_addressId, 
           address1 = a.new_AddressLine1, 
           address2 = a.new_AddressLine2, 
           address3 = a.new_AddressLine3, 
           address4 = a.new_AddressLine4, 
           county = cy.new_County 
          }; 

任何幫助將不勝感激，

感謝， 尼爾

編輯：

我也試過使用'進入'的聲明，但後來在我的第二次加入別名是不承認。

from pm in ContextService.CreateQuery<new_partialmatch>() 
          join c in ContextService.CreateQuery<new_client>()  on pm.new_ClientId.Id equals c.new_clientId into pmc 
          from x in pmc.DefaultIfEmpty() 
          join a in ContextService.CreateQuery<new_address>() on c.new_AddressID.Id equals a.new_addressId 

所以對於c.newIddressID.Id等於a.new_addressId我收到此錯誤信息：

名「C」是不是在範圍上的「等於」左側。考慮交換'equals'兩邊的表達式。

Answer 1

var addressCountryQuery = from a in ContextService.CreateQuery<new_address>() 
          from cy in ContextService.CreateQuery<new_county>().Where(cy => cy.new_countyId == a.new_CountyID.Id).DefaultIfEmpty() 
          select new 
          { 
           addressId = a.new_addressId, 
           address1 = a.new_AddressLine1, 
           address2 = a.new_AddressLine2, 
           address3 = a.new_AddressLine3, 
           address4 = a.new_AddressLine4, 
           county = cy.new_County 
          } 

var partialMatches = from pm in ContextService.CreateQuery<new_partialmatch>() 
        join c in ContextService.CreateQuery<new_client>()  on pm.new_ClientId.Id equals c.new_clientId 
        from a in addressCountryQuery .Where(a => a.addressId == c.new_AddressID.Id).DefaultIfEmpty() 
          where pm.OwnerId.Id == _currentUserId && pm.new_Reviewed != true 

          select new 
          { 
           Id = pm.Id, 
           new_ClientID = pm.new_ClientId, 
           new_MatchingCRMClientID = pm.new_MatchingCRMClientId, 
           new_MatchingVulcanClientID = pm.new_MatchingVulcanClientID, 
           new_name = pm.new_name, 
           firstname = c.new_FirstName, 
           surname = c.new_Surname, 
           dob = c.new_DateOfBirth, 
           addressId = a.addressId, 
           address1 = a.AddressLine1, 
           address2 = a.AddressLine2, 
           address3 = a.AddressLine3, 
           address4 = a.AddressLine4, 
           county = a.County 
          }; 

看看我如何修改a和cy的連接，所以我可以添加DefultIfEmpty方法。

我將兩個外部連接拆分爲一個查詢，然後將該查詢連接回原始查詢。