如何改進此LINQ TO SQL可查詢？

我有一個學生名單，我想正如我在下面的代碼創建一個查詢，在那裏得到所有的項目，而不是由1：如何改進此LINQ TO SQL可查詢？

  IEnumerable<Student> = ... 
      List<AnsweredTest> ats = new List<AnsweredTest>(); 

      foreach (var s in students) 
      { 
       query = from at in Database.Current.AnsweredTests 
         where at.StudentId == s.StudentId 
         select at; 

       ats.Add(query.Single()); 
      } 

      listView.ItemsSource = ats;

這是不好的表現。我希望讓自己清楚，如果不是，請讓我知道。

來源

2013-01-07 Darf Zon

要麼做一個加入：

query = from at in Database.Current.AnsweredTests 
    join s in Database.Current.Students on at.StudentId == s.StudentId 
    where s... // filter s if needed. 
    select at;

或者搶學生證的名單，並將其傳遞到查詢：

int[] studentIds = students.Select(s => s.StudentId).ToArray(); 
    query = from at in Database.Current.AnsweredTests 
    where studentIds.Any(id => at.StudentId == id) 
    select at;

來源

2013-01-07 21:13:14 jessehouwing

這個工程！在另一個答案我收到這樣的錯誤：http://stackoverflow.com/questions/10862491/unable-to-create-a-constant-value-only-primitive-types –

var ats = Database.Current.AnsweredTests 
    .Where(at => students.Any(s => s.StudentId == at.StudentId).ToList()

來源

2013-01-07 21:11:05 lante

也許是這樣的：

var studentIds = students.Select(s => s.StudentId); 
var ats = Database.Current.AnsweredTests.Where(at => studentIds.Contains(at.StudentId));

來源

2013-01-07 21:19:48

如何改進此LINQ TO SQL可查詢？

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