概述: 在CompletedQuestions表中,UserId對應於完成該問題的用戶。 Id屬性對應於「問題」表中的其中一個問題。我知道,我沒有正確指定關係。但我不是很有經驗。我只想完成一個項目,然後我會回來修復那些不好的編碼實踐,一旦我瞭解更多。我無法理解以下例外情況。LINQ to Entities不識別方法
LINQ to Entities does not recognize the method 'Riddle.Models.CompletedQuestion LastOrDefault[CompletedQuestion](System.Linq.IQueryable`1[Riddle.Models.CompletedQuestion])' method, and this method cannot be translated into a store expression.
Line 46: if (RiddleCompleted == null)
Line 47: {
Line 48: var lastCompletedQuestion = _db.CompletedQuestions.Where(q => q.UserId == currentUserId) // exception occurs in this line
Line 49: .OrderBy(q => q.QuestionNumber)
Line 50: .LastOrDefault();
在異常發生的動作:
public ActionResult Riddle(int Id)
{
string currentUserId = User.Identity.GetUserId();
var riddle = _db.Riddles.Where(r => r.Id == Id).Single();
if (riddle.User.Id == User.Identity.GetUserId())
{
var question = riddle.Questions.Where(q => q.QuestionNumber == 1).SingleOrDefault();
if (question == null)
{
return View("NoMoreQuestions");
}
return View("RiddleOwner", question);
}
else
{
var RiddleCompleted = _db.CompletedRiddles.Where(r => r.Id == Id && r.UserId == currentUserId).SingleOrDefault();
if (RiddleCompleted == null)
{
var lastCompletedQuestion = _db.CompletedQuestions.Where(q => q.UserId == currentUserId) // exception occurs in this line
.OrderBy(q => q.QuestionNumber)
.LastOrDefault();
if (lastCompletedQuestion == null)
{
var question = riddle.Questions.Where(q => q.QuestionNumber == 1).Single();
return View(question);
}
else
{
var question = riddle.Questions.Where(q => q.QuestionNumber == lastCompletedQuestion.QuestionNumber + 1).SingleOrDefault();
return View(question);
}
}
else
{
return View("NoMoreQuestions");
}
}
}
CompletedQuestion型號:
public class CompletedQuestion
{
public int Id { get; set; }
public string UserId { get; set; }
public int QuestionNumber { get; set; }
}
問題型號:
public class Question
{
public int Id { get; set; }
public string Body { get; set; }
public string Answer { get; set; }
public Riddle Riddle { get; set; }
[Column(TypeName ="datetime2")]
public DateTime CreationDate { get; set; }
public int QuestionNumber { get; set; }
}