LINQ: From a list of type T, retrieve only objects of a certain subclass S

c# linq typeof oftype
Hythloth picture Hythloth · Jul 26, 2009 · Viewed 33.6k times · Source

Given a simple inheritance hierarchy: Person -> Student, Teacher, Staff

Say I have a list of Persons, L. In that list are some Students, Teachers, and Staff.

Using LINQ and C#, is there a way I could write a method that could retrieve only a particular type of person?

I know I can do something like:

var peopleIWant = L.OfType< Teacher >();

But I want to be able to do something more dynamic. I would like to write a method that will retrieve results for any type of Person I could think of, without having to write a method for every possible type.

Answer

Mladen Prajdic picture Mladen Prajdic · Jul 26, 2009

you can do this:

IList<Person> persons = new List<Person>();

public IList<T> GetPersons<T>() where T : Person
{
    return persons.OfType<T>().ToList();
}

IList<Student> students = GetPersons<Student>();
IList<Teacher> teacher = GetPersons<Teacher>();

EDIT: added the where constraint.

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