CODEWITHSUNDEEP
c#
A Bogus
A Bogus

Reputation: 3930

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

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 those items to their own List<>.

This is not working -

//myAbstractItems is a List<myAbstractItem>
//typeAList inherents from myAbstractItem


var typeAList = ((List<itemTypeA>)myAbstractItems.Where(i => i.GetType() == typeof(itemTypeA)).ToList());

The casting (List<itemTypeA>) appears to be failing.

Upvotes: 6

Views: 2543

Answers (5)

Kristian Fenn
Kristian Fenn

Reputation: 867

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.

Upvotes: 0

KeithS
KeithS

Reputation: 71573

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.

Upvotes: 0

Haris Hasan
Haris Hasan

Reputation: 30097

Try using Where this way:

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

Upvotes: 0

Lance U. Matthews
Lance U. Matthews

Reputation: 16612

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.

Upvotes: 13

Benjamin Baumann
Benjamin Baumann

Reputation: 4065

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)
}

Upvotes: 0

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