在linq查詢中使用子查詢

Question

如何在linq查詢中構造下面的sql查詢以獲取結果？

SELECT PageNumber from LMS_SurveyQuestion WHERE SurveyQuestionID IN 
(SELECT SurveyQuestionID from LMS_SurveyQuestionOptionChoice 
WHERE NextPageNumber = 4) and SurveyID = 1 

Answer 1

看一看this article。基本上，如果你想在LINQ中實現SQL IN查詢，你需要首先構造一個內部查詢，然後使用Contains（）方法。這是我的嘗試：

var innerQuery = (from log in LMS_SurveyQuestionOptionChoice where log.NextPageNumber = 4 select log.SurveyQuestionID); 

var result = (from f in LMS_SurveyQuestion where innerQuery.Contains(f.SurveyQuestionID) && f.SurveyID = 1 select f); 

希望這會有所幫助。

Answer 2

試試這個

var result = from l in LMS_SurveyQuestion 
      let lsq = from l_S in LMS_SurveyQuestionOptionChoice 
      where l_S.NextPageNumber = 4 
      select l_S.SurveyQuestionID 
      where lsq.Contains(l.SurveyQuestionID) and l.surveyid = 1 
      select l.PageNumber;