Lambda 表达式 where id 在 id 列表中

Question

我有 2 个列表

var listquestionold = db.tblExamQuetions.Where(p => p.QuetionExamId == oldexamid).ToList();
var listquestionnew = listquestionnew = db.tblExamQuetions.Where(p => p.QuetionExamId == examid ).ToList();
List<tblExamQuestionAnswers> listanswers = new List<tblExamQuestionAnswers>();

我怎样才能得到questionId 在listquestionold 中的答案： listanswers =db.tblanswers.where(p=> p.ExamQuestionId exists in listquestionold?

Answer 1

使用List 的Contains 方法很容易：

var listquestionold = db.tblExamQuetions.Where(p => p.QuetionExamId == oldexamid).ToList();
var listanswers = db.tblanswers.Where(w => listquestionold.Contains(w.ExamQuestionId)).ToList();