How to generate a not in statement using LINQ or EF

For example, there is a questionnaire table questionnaire and an activity-questionnaire relationship table activityoption_questionnaire. Now we need to find a questionnaire that is not in the activity.

The implementation method with EF is as follows:

VaR notin = dB. Questionnaires. Where (A =>! (Db. activityoption_questionnaire_s.select (B => B. questionnaireid). Contains (A. ID )));

 

 

Use the following method to implement the function:

VaR notin = from a in questionnaire
Where! (From B in db. activityoption_questionnaire_s select B. questionnaireid). Contains (A. ID ))
Select;

How to generate a not in statement using LINQ or EF