LINQ的WHERE子句其中COLUMN可能爲空

Question

我有用LINQ製作WHERE子句的問題。我試圖谷歌它，但我只有如何處理如果外部變量是可空的整數類型的答案......嗯，我試過這些方法相反（我有0 ... 1關係在我的數據集中）： 例如

int oldId = oldQuestion.id; 
IEnumerable<possible_answer> possibleAnswersQuery = 
      from x in Mentor11Entities.possible_answers 
      where object.Equals(x.question_id, oldId) 
      select x; 
List<possible_answer> possibleAnswers = 
      possibleAnswersQuery.ToList<possible_answer>(); 

或

int oldId = oldQuestion.id; 
IEnumerable<possible_answer> possibleAnswersQuery = 
      from x in Mentor11Entities.possible_answers 
      where Convert.ToInt32(x.question_id ?? 0).Equals(oldId) 
      select x; 
List<possible_answer> possibleAnswers = 
      possibleAnswersQuery.ToList<possible_answer>(); 

，但我一直都想與這LINQ不支持某些功能的錯誤......有沒有什麼辦法來解決這個問題？

Answer 1

只使用

where x.question_id != null && x.question_id == oldId 

所以您的查詢應該是：

IEnumerable<possible_answer> possibleAnswersQuery = 
      from x in Mentor11Entities.possible_answers 
      where x.question_id != null && x.question_id == oldId 
      select x;