Question

Instead of using Dictionary<TKey,TValue> I want some type of collection class that can use a property of the value as the key, is there something like this?

Answer 1

Yes, there is – System.Collections.ObjectModel.KeyedCollection<TKey, TValue>.

That’s abstract, and there are no concrete derived classes in the framework as far as I can see, but all you need to implement is GetKeyForItem as far as I can see. For example, you could do this with a delegate:

public class DelegatingKeyedCollection<TKey, TItem> : System.Collections.ObjectModel.KeyedCollection<TKey, TItem>
{
    private readonly Func<TItem, TKey> keySelector;

    public DelegatingKeyedCollection(Func<TItem, TKey> keySelector)
    {
        this.keySelector = keySelector;
    }

    protected override TKey GetKeyForItem(TItem item)
    {
        return keySelector(item);
    }
}