Lookup<K, E>
using System.Collections;
using System.Collections.Generic;
using System.Linq;
namespace System.Reactive
{
internal sealed class Lookup<K, E> : ILookup<K, E>, IEnumerable<IGrouping<K, E>>, IEnumerable
{
private sealed class Grouping : IGrouping<K, E>, IEnumerable<E>, IEnumerable
{
private readonly KeyValuePair<K, List<E>> _keyValuePair;
public K Key => _keyValuePair.Key;
public Grouping(KeyValuePair<K, List<E>> keyValuePair)
{
_keyValuePair = keyValuePair;
}
public IEnumerator<E> GetEnumerator()
{
return _keyValuePair.Value.GetEnumerator();
}
IEnumerator IEnumerable.GetEnumerator()
{
return GetEnumerator();
}
}
private readonly Dictionary<K, List<E>> _dictionary;
public int Count => _dictionary.Count;
public IEnumerable<E> this[K key] {
get {
if (!_dictionary.TryGetValue(key, out List<E> value))
return Enumerable.Empty<E>();
return Hide(value);
}
}
public Lookup(IEqualityComparer<K> comparer)
{
_dictionary = new Dictionary<K, List<E>>(comparer);
}
public void Add(K key, E element)
{
if (!_dictionary.TryGetValue(key, out List<E> value))
value = (_dictionary[key] = new List<E>());
value.Add(element);
}
public bool Contains(K key)
{
return _dictionary.ContainsKey(key);
}
private static IEnumerable<E> Hide(List<E> elements)
{
return Enumerable.Skip<E>((IEnumerable<E>)elements, 0);
}
public IEnumerator<IGrouping<K, E>> GetEnumerator()
{
Dictionary<K, List<E>>.Enumerator enumerator = this._dictionary.GetEnumerator();
try {
while (enumerator.MoveNext()) {
KeyValuePair<K, List<E>> current = enumerator.Current;
yield return (IGrouping<K, E>)new Grouping(current);
}
} finally {
((IDisposable)enumerator).Dispose();
}
enumerator = default(Dictionary<K, List<E>>.Enumerator);
}
IEnumerator IEnumerable.GetEnumerator()
{
return GetEnumerator();
}
}
}