Return a list of objects of class that implements and interface [duplicate]

This question already has an answer here:

• creating instance of a type dynamically 1 answer

Say I have a class structure like this:

public class Student
{

}

public class Undergraduate : Student
{

}

public class Postgraduate : Student
{

}

Is it possible to return an instance of all the classes that inherit from Student in a list like this:

List<Student> Student = new List<Student>

I am wandering if this can be done using reflection:

Student.Add(new PostGraduate);
Student.Add(new UnderGraduate);

I believe I have to use reflection for this. I have tried this:

var type = typeof(Student);
var types = AppDomain.CurrentDomain.GetAssemblies()
    .SelectMany(s => s.GetTypes())
    .Where(p => type.IsAssignableFrom(p));

However, this does not return a type of Undergraduate and a type of graduate in a list.