IEnumerable implementation only for Dictionary values

Question

I have a class, let's say Player, with a name and some attributes:

public class Players
{
    public string PlayerName { get; set; }
    public IList<Goal> Goals { get; set; }
    ...
}

I want to create a custom collection class, PlayerCollection, but using a Dictionary instead of a list for quicker search. So:

public class PlayersCollection
{
    private readonly IDIctionary<string, Player> _players;
    ....

Using a dictionary with the player name as the key will make things easier in the rest of my program. Now I'd like to implement IEnumerable<Player>, in order to iterate over the player class, but I can't use the dictionary's enumerator, because it is implemented on KeyValuePair<string, Player>.

How can I do that?

`Dictionary` implements same `IEnumerable` as List, just that each element is element is a KeyValuePair, and here Key will be name and Value will be Object — Mrinal Kamboj, Nov 12 '16 at 16:18
Any special reason for having a custom `IEnumerable`, there are no same existing collections, which can be effectively used — Mrinal Kamboj, Nov 12 '16 at 16:23

YuvShap · Answer 1 · 2016-11-12T16:29:28.257

3

Try this:

public class PlayersCollection : IEnumerable<Player>
{
    private readonly IDictionary<string, Player> _players;

    public IEnumerator<Player> GetEnumerator()
    {
        return _players.Select(player => player.Value).GetEnumerator();
    }
}

If you are looking for a collection with a quick search I suggest you to read about HashSet<T> which is part of the framework.

edited Nov 12 '16 at 16:29

answered Nov 12 '16 at 16:16

YuvShap

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Actually you should be able to use .Values instead of selecting the values. Performance will be improved – Phate01 Nov 12 '16 at 19:38

score 2 · Accepted Answer · answered Nov 12 '16 at 16:32

The KeyedCollection class is perfect for your situation. It lets you look up by a property of members of the collection. The only thing you need to do is create a derived class that has a selector for the property.

public class PlayersCollection : KeyedCollection<string, Players>
{
    protected override string GetKeyForItem(Players item)
    {
        return item.PlayerName;
    }
}

When you get the enumerator for the PlayersCollection it will be a IEnumerable<Players>.

IEnumerable implementation only for Dictionary values

2 Answers2