Question

I have a collection which contains two type of objects A & B.

Class Base{}
Class A : Base {}
Class B : Base {}

List<Base> collection = new List<Base>();
collection.Add(new A());
collection.Add(new B());
collection.Add(new A());
collection.Add(new A());
collection.Add(new B());

Now I want to select the objects from the collection based on its type (A or B, not both).

How I can write a LINQ query for this? Otherwise I need to loop through the collection, which I don’t want to.

Edit:

Thank you all for your help. Now I can use OfType() from LINQ. But I think in my case it won’t work. My situation is

Class Container
{
  List<Base> bases;
}

List<Container> containers = new List<Container>();

Now I want to select the container from containers, which has at least one type A. Maybe this can’t be done by LINQ.

Answer 1

You can use the OfType Linq method for that:

var ofTypeA = collection.OfType<A>();

Regarding your unwillingness to loop throught the collection, you should keep in mind that Linq does not do magic tricks; I didn’t check the implementation of OfType, but I would be surprised not to find a loop or iterator in there.