LINQ表達式具有多個與條件聯接在每個加入

Question

我有這樣的表的數目：

1. User_cs
2. UserEducation_cs
3. 經驗

以下是數據庫圖表

我需要的是用戶信息

1. 他們從User_cs獲取的基本信息
2. 他們上一次接受的教育（即：他們獲得的最新學歷）
3. Experience_cs中他們當前正在工作的位置（如果用戶不在工作的話）將爲NULL。

我到目前爲止能夠做到以下，但我遇到了麻煩1）我如何在lamda表達式中做（IsWorking == true）並且跟隨那個連接到下一個表。以下是我的表達

List<Models.UserInfo> v = context.User_cs 
      .Join(context.UserEducation_cs, u => u.UserName, ue => ue.UserName, (u, ue) => new UserEducation_cs 
      { 
       UserName = ue.UserName, 
       EducationId = ue.EducationId, 
       StartDate = ue.StartDate, 
       EndDate = ue.EndDate 
      }). 
      Join(context.Education_cs, ue => ue.EducationId, e => e.EducationId, (ue, e) => new 
      { 
       UserName = ue.UserName, 
       EducationId = ue.EducationId, 
       StartDate = ue.StartDate, 
       EndDate = ue.EndDate, 
       Title = e.Title, 
       Major = e.Major, 
       MajorDetails = e.MajorDetails, 
       Info = e.Info 
      }). 
      Join(context.Experiences, lst => lst.UserName, ex => ex.UserName, (lst, ex) => new Models.UserInfo 
      { 
       UserName = ex.UserName, 
       EducationId = lst.EducationId, 
       StartDate = lst.StartDate, 
       EndDate = lst.EndDate, 
       Title = lst.Title, 
       Major = lst.Major, 
       MajorDetails = lst.MajorDetails, 
       Info = lst.Info, 
       IsWorking = ex.IsWorking, 
       StartDate_ex=ex.StartedDate,      
      }). 
      Where(iw => iw.IsWorking == true).ToList(); 

任何幫助將不勝感激

Answer 1

我不能完全肯定，如果我完全理解你的問題。我認爲你需要在應用（內部）連接之前過濾你的列表。爲了得到每個User_cs只有最新的Education_cs條目，我想你可以使用分組。此外，我還沒有完全測試此代碼：

List<Models.UserInfo> v = context.User_cs 
     .Join(context.UserEducation_cs, u => u.UserName, ue => ue.UserName, (u, ue) => new UserEducation_cs 
     { 
      UserName = ue.UserName, 
      EducationId = ue.EducationId, 
      StartDate = ue.StartDate, 
      EndDate = ue.EndDate 
     }). 
     Join(context.Education_cs.GroupBy(q => q.UserName).Select(q => q.OrderByDescending(w => w.StartDate).First()), 
      ue => ue.EducationId, e => e.EducationId, (ue, e) => new 
     { 
      UserName = ue.UserName, 
      EducationId = ue.EducationId, 
      StartDate = ue.StartDate, 
      EndDate = ue.EndDate, 
      Title = e.Title, 
      Major = e.Major, 
      MajorDetails = e.MajorDetails, 
      Info = e.Info 
     }). 
     Join(context.Experiences.Where(ex => ex.IsWorking), lst => lst.UserName, ex => ex.UserName, (lst, ex) => new Models.UserInfo 
     { 
      UserName = ex.UserName, 
      EducationId = lst.EducationId, 
      StartDate = lst.StartDate, 
      EndDate = lst.EndDate, 
      Title = lst.Title, 
      Major = lst.Major, 
      MajorDetails = lst.MajorDetails, 
      Info = lst.Info, 
      IsWorking = ex.IsWorking, 
      StartDate_ex=ex.StartedDate,      
     }).ToList();