Linq查询从Ilist <>转换为List <>

Question

I receive IList<> data and stores them like this:

 IList<Student> StudentList = DataKilde.Studenter();

Now I want to read them into a List<Student> :

List<Student> studentWhere3 = StudentList.Where(x=> x.StudentId > 2 && x.StudentId < 8).ToList(); 

This is working...becoz I think .ToList converts it to Ilist<> to List<> ?

My problem is, when I am doing this:

List<Student> studentWhere5 = from s in StudentList
                              where s.StudentId==2
                              select s

I get a conversion error and have tried these:

from s in (List<Student>)StudentList

from s in StudentList as List<Student>

But it's not working.. I don't get why ?

Answer 1

That's because select s returns an IQueryable<Student> , which is not implicitly nor explicitly convertable to a List<Student> , because there is no inheritance between the two.

You need to materialize the query result into a list:

(from s in StudentList
where s.StudentId==2
select s).ToList();

This will take all elements from the source collection ( s ) and store them in a List<Student> , which implements IList<Student> .