在linq查询中使用子查询

Question

如何在linq查询中构造下面的sql查询以获取结果？

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中实现SQL IN查询，你需要首先构造一个内部查询，然后使用Contains（）方法。这是我的尝试：

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); 

希望这会有所帮助。

Answer 2

试试这个

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;