CODEWITHSUNDEEP
c#linqcollections
subs
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Reputation: 2249

Creating a collection of a particular property of all the elements of a collection without iterating the elements of that collection

I have a treenode collection as IEnumerable<treenode> nodes. Is there any method to create a collection of treenode.guid directly from nodes without iterating all the elements?

E.g.:

guidcollection nodeguids = nodes.somemethod();

Upvotes: 0

Views: 69

Answers (2)

Andrei
Andrei

Reputation: 56688

The answer is not - you obviously need to iterate through the collection of nodes if you need some info from each of them. However you can do something like:

IEnumerable<Guid> nodeguids = nodes.Select(n => n.Id);

This way you do not perform an iteration manually at least. Although implementation of Select involves iteration over all the elements of the collection, and it will be done at the moment you will try to use the nodeguids collection somewhere.

Upvotes: 3

Jarrett Meyer
Jarrett Meyer

Reputation: 19583

LINQ uses a lazy iterator. So you can create a collection like this...

IEnumerable<TreeNode> myCollection = GetTreeNodes();
IEnumerable<Guid> guidCollection = myCollection.Select(tn => tn.Guid);

The guidCollection will not be populated until it is iterated, counted, acted upon in some way.

You could also just go old school.

function IEnumerable<Guid> GetIdsFromCollection(TreeNode collection)
{
    foreach (var item in collection)
        yield return item;
}

Upvotes: 0

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