ln.collections/ln.collections/WeakValueDictionary.cs

// /**
//  * File: WeakValueDictionary.cs
//  * Author: haraldwolff
//  *
//  * This file and it's content is copyrighted by the Author and / or copyright holder.
//  * Any use wihtout proper permission is illegal and may lead to legal actions.
//  *
//  *
//  **/
using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
namespace ln.collections
{
    public class WeakValueDictionary<K,V> : IDictionary<K,V> where V:class
    {
        Dictionary<K, WeakReference<V>> keyValues = new Dictionary<K, WeakReference<V>>();

        public WeakValueDictionary()
        {
        }

        public V this[K key] {
            get => TryGetValue(key, out V value) ? value : throw new KeyNotFoundException();
            set => SetValue(key, value);
        }

        public ICollection<K> Keys => keyValues.Keys;
        public ICollection<V> Values
        {
            get
            {
                List<V> values = new List<V>();

                foreach (K key in Keys.ToArray())
                {
                    WeakReference<V> weakValue = keyValues[key];
                    if (weakValue.TryGetTarget(out V value))
                    {
                        values.Add(value);
                    }
                    else
                    {
                        keyValues.Remove(key);
                    }
                }

                return values;
            }
        }

        public int Count => keyValues.Count;
        public bool IsReadOnly => false;

        public void Add(KeyValuePair<K, V> item) => Add(item.Key, item.Value);
        public void Add(K key, V value)
        {
            if (keyValues.ContainsKey(key))
                throw new ArgumentException();

            SetValue(key, value);
        }

        public void Clear() => keyValues.Clear();
        public bool Contains(KeyValuePair<K, V> item)
        {
            if (TryGetValue(item.Key,out V value))
            {
                return Equals(item.Value, value);
            }
            return false;
        }

        public bool ContainsKey(K key) => keyValues.ContainsKey(key);
        public void CopyTo(KeyValuePair<K, V>[] array, int arrayIndex)
        {
            foreach (KeyValuePair<K,WeakReference<V>> kvp in keyValues)
            {
                if (kvp.Value.TryGetTarget(out V value))
                    array[arrayIndex++] = new KeyValuePair<K, V>(kvp.Key, value);
            }
        }

        public IEnumerator<KeyValuePair<K, V>> GetEnumerator()
        {
            foreach (KeyValuePair<K, WeakReference<V>> kvp in keyValues)
            {
                if (kvp.Value.TryGetTarget(out V value))
                    yield return new KeyValuePair<K, V>(kvp.Key, value);
            }
        }

        public bool Remove(K key) => keyValues.Remove(key);
        public bool Remove(KeyValuePair<K, V> item) => Remove(item.Key);

        public bool TryGetValue(K key, out V value)
        {
            if (keyValues.TryGetValue(key, out WeakReference<V> weakValue))
            {
                if (weakValue.TryGetTarget(out value))
                    return true;

                keyValues.Remove(key);
            }

            value = null;
            return false;
        }
        public bool SetValue(K key,V value)
        {
            keyValues[key] = new WeakReference<V>(value);
            return true;
        }

        IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
    }
}