Get all items of a certain type from a List of abstract type

Question

I have a List<> of abstract objects that contains different types of objects. I am trying to grab all the items of a certain type and set th

Answer 1

This will work for all itemTypeAs (and more derived types).

var typeAList = myAbstractItems.Select(i => i as itemTypeA).Where(i => i != null).ToList();

EDIT: edited as per Rawling's comment.

Answer 2

A good old loop should be fine :

List<itemTypeA> res = new List<itemTypeA>();
foreach(var item in myAbstractItems)
{
  itemTypeA temp = item as itemTypeA;
  if (temp != null)
    res.Add(temp)
}

Answer 3

Try using Where this way:

var typeAList = myAbstractItems.Where(i => i.GetType() == typeof(itemTypeA)).Select(item => item as itemTypeA).ToList())

Answer 4

Another way you could do this is using the OfType() method:

var typeAList = myAbstractItems.OfType<itemTypeA>().ToList();

This method basically performs the following operation:

var typeAList = myAbstractItems.Where(i=>i is itemTypeA).Select(i=>i as itemTypeA).ToList();

Keep in mind that this will fail if any element of the source collection is a null reference.

Answer 5

Use the OfType extension method:

var typeAList = myAbstractItems.OfType<itemTypeA>().ToList();

From the documentation...

The OfType(IEnumerable) method returns only those elements in source that can be cast to type TResult.