linq query for join 2 collection

Question

Q1>I have 2 dto like

List<SecurityQuestionsSetDto>

{

questionsetid;

questionsetname;

questionsetdesc;

List<SecurityQuestionsDto>

}

 

In List<SecurityQuestionsDto>

the properities are 

{

QuestionId;

QuestionText

 }

For this i want to join using linq.The out put should be first dto under the list the child property r there.