关于.NET:C#中的双向1到1字典

Bidirectional 1 to 1 Dictionary in C#

我在C(2)中寻找一个通用的、双向的1到1字典类,即BiDictionaryOneToOne,它保证只包含每个值和键中的一个(无论如何最多可包含refequals),并且可以使用键或值进行搜索。有人知道吗,还是我自己来实现?我不敢相信我是第一个需要这个的人…

这个问题的答案中有一个bidictionary,但它不是针对唯一元素(也不实现removebyfirst(t t)或removebysecond(s))。

谢谢!


好的,这是我的尝试(建立在Jon的基础上-谢谢),存档在这里并打开进行改进:

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/// <summary>
/// This is a dictionary guaranteed to have only one of each value and key.
/// It may be searched either by TFirst or by TSecond, giving a unique answer because it is 1 to 1.
/// </summary>
/// <typeparam name="TFirst">The type of the"key"</typeparam>
/// <typeparam name="TSecond">The type of the"value"</typeparam>
public class BiDictionaryOneToOne<TFirst, TSecond>
{
    IDictionary<TFirst, TSecond> firstToSecond = new Dictionary<TFirst, TSecond>();
    IDictionary<TSecond, TFirst> secondToFirst = new Dictionary<TSecond, TFirst>();

    #region Exception throwing methods

    /// <summary>
    /// Tries to add the pair to the dictionary.
    /// Throws an exception if either element is already in the dictionary
    /// </summary>
    /// <param name="first"></param>
    /// <param name="second"></param>
    public void Add(TFirst first, TSecond second)
    {
        if (firstToSecond.ContainsKey(first) || secondToFirst.ContainsKey(second))
            throw new ArgumentException("Duplicate first or second");

        firstToSecond.Add(first, second);
        secondToFirst.Add(second, first);
    }

    /// <summary>
    /// Find the TSecond corresponding to the TFirst first
    /// Throws an exception if first is not in the dictionary.
    /// </summary>
    /// <param name="first">the key to search for</param>
    /// <returns>the value corresponding to first</returns>
    public TSecond GetByFirst(TFirst first)
    {
        TSecond second;
        if (!firstToSecond.TryGetValue(first, out second))
            throw new ArgumentException("first");

        return second;
    }

    /// <summary>
    /// Find the TFirst corresponing to the Second second.
    /// Throws an exception if second is not in the dictionary.
    /// </summary>
    /// <param name="second">the key to search for</param>
    /// <returns>the value corresponding to second</returns>
    public TFirst GetBySecond(TSecond second)
    {
        TFirst first;
        if (!secondToFirst.TryGetValue(second, out first))
            throw new ArgumentException("second");

        return first;
    }


    /// <summary>
    /// Remove the record containing first.
    /// If first is not in the dictionary, throws an Exception.
    /// </summary>
    /// <param name="first">the key of the record to delete</param>
    public void RemoveByFirst(TFirst first)
    {
        TSecond second;
        if (!firstToSecond.TryGetValue(first, out second))
            throw new ArgumentException("first");

        firstToSecond.Remove(first);
        secondToFirst.Remove(second);
    }

    /// <summary>
    /// Remove the record containing second.
    /// If second is not in the dictionary, throws an Exception.
    /// </summary>
    /// <param name="second">the key of the record to delete</param>
    public void RemoveBySecond(TSecond second)
    {
        TFirst first;
        if (!secondToFirst.TryGetValue(second, out first))
            throw new ArgumentException("second");

        secondToFirst.Remove(second);
        firstToSecond.Remove(first);
    }

    #endregion

    #region Try methods

    /// <summary>
    /// Tries to add the pair to the dictionary.
    /// Returns false if either element is already in the dictionary        
    /// </summary>
    /// <param name="first"></param>
    /// <param name="second"></param>
    /// <returns>true if successfully added, false if either element are already in the dictionary</returns>
    public Boolean TryAdd(TFirst first, TSecond second)
    {
        if (firstToSecond.ContainsKey(first) || secondToFirst.ContainsKey(second))
            return false;

        firstToSecond.Add(first, second);
        secondToFirst.Add(second, first);
        return true;
    }


    /// <summary>
    /// Find the TSecond corresponding to the TFirst first.
    /// Returns false if first is not in the dictionary.
    /// </summary>
    /// <param name="first">the key to search for</param>
    /// <param name="second">the corresponding value</param>
    /// <returns>true if first is in the dictionary, false otherwise</returns>
    public Boolean TryGetByFirst(TFirst first, out TSecond second)
    {
        return firstToSecond.TryGetValue(first, out second);
    }

    /// <summary>
    /// Find the TFirst corresponding to the TSecond second.
    /// Returns false if second is not in the dictionary.
    /// </summary>
    /// <param name="second">the key to search for</param>
    /// <param name="first">the corresponding value</param>
    /// <returns>true if second is in the dictionary, false otherwise</returns>
    public Boolean TryGetBySecond(TSecond second, out TFirst first)
    {
        return secondToFirst.TryGetValue(second, out first);
    }

    /// <summary>
    /// Remove the record containing first, if there is one.
    /// </summary>
    /// <param name="first"></param>
    /// <returns> If first is not in the dictionary, returns false, otherwise true</returns>
    public Boolean TryRemoveByFirst(TFirst first)
    {
        TSecond second;
        if (!firstToSecond.TryGetValue(first, out second))
            return false;

        firstToSecond.Remove(first);
        secondToFirst.Remove(second);
        return true;
    }

    /// <summary>
    /// Remove the record containing second, if there is one.
    /// </summary>
    /// <param name="second"></param>
    /// <returns> If second is not in the dictionary, returns false, otherwise true</returns>
    public Boolean TryRemoveBySecond(TSecond second)
    {
        TFirst first;
        if (!secondToFirst.TryGetValue(second, out first))
            return false;

        secondToFirst.Remove(second);
        firstToSecond.Remove(first);
        return true;
    }

    #endregion        

    /// <summary>
    /// The number of pairs stored in the dictionary
    /// </summary>
    public Int32 Count
    {
        get { return firstToSecond.Count; }
    }

    /// <summary>
    /// Removes all items from the dictionary.
    /// </summary>
    public void Clear()
    {
        firstToSecond.Clear();
        secondToFirst.Clear();
    }
}


更完整的双向字典实现:

  • 几乎支持原始Dictionary的所有接口(基础设施接口除外):
    • IDictionary
    • IReadOnlyDictionary
    • IDictionary
    • ICollection>(本界面及以下为上述界面的基础界面)
    • ICollection
    • IReadOnlyCollection>
    • IEnumerable>
    • IEnumerable
  • 使用SerializableAttribute进行序列化。
  • 使用DebuggerDisplayAttributeDebuggerTypeProxyAttribute调试视图(用于在手表中显示键值对)。
  • Reverse Dictionary作为IDictionary Reverse属性提供,也实现了上面提到的所有接口。任何一个字典上的所有操作都会同时修改这两个字典。

用途:

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var dic = new BiDictionary<int, string>();
dic.Add(1,"1");
dic[2] ="2";
dic.Reverse.Add("3", 3);
dic.Reverse["4"] = 4;
dic.Clear();

代码在我的Github私有框架中提供:bidictionary(tfirst,tsecond).cs(permalink,search)。

复印件:

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[Serializable]
[DebuggerDisplay ("Count = {Count}"), DebuggerTypeProxy (typeof(DictionaryDebugView<,>))]
public class BiDictionary<TFirst, TSecond> : IDictionary<TFirst, TSecond>, IReadOnlyDictionary<TFirst, TSecond>, IDictionary
{
    private readonly IDictionary<TFirst, TSecond> _firstToSecond = new Dictionary<TFirst, TSecond>();
    [NonSerialized]
    private readonly IDictionary<TSecond, TFirst> _secondToFirst = new Dictionary<TSecond, TFirst>();
    [NonSerialized]
    private readonly ReverseDictionary _reverseDictionary;

    public BiDictionary ()
    {
        _reverseDictionary = new ReverseDictionary(this);
    }

    public IDictionary<TSecond, TFirst> Reverse
    {
        get { return _reverseDictionary; }
    }

    public int Count
    {
        get { return _firstToSecond.Count; }
    }

    object ICollection.SyncRoot
    {
        get { return ((ICollection)_firstToSecond).SyncRoot; }
    }

    bool ICollection.IsSynchronized
    {
        get { return ((ICollection)_firstToSecond).IsSynchronized; }
    }

    bool IDictionary.IsFixedSize
    {
        get { return ((IDictionary)_firstToSecond).IsFixedSize; }
    }

    public bool IsReadOnly
    {
        get { return _firstToSecond.IsReadOnly || _secondToFirst.IsReadOnly; }
    }

    public TSecond this [TFirst key]
    {
        get { return _firstToSecond[key]; }
        set
        {
            _firstToSecond[key] = value;
            _secondToFirst[value] = key;
        }
    }

    object IDictionary.this [object key]
    {
        get { return ((IDictionary)_firstToSecond)[key]; }
        set
        {
            ((IDictionary)_firstToSecond)[key] = value;
            ((IDictionary)_secondToFirst)[value] = key;
        }
    }

    public ICollection<TFirst> Keys
    {
        get { return _firstToSecond.Keys; }
    }

    ICollection IDictionary.Keys
    {
        get { return ((IDictionary)_firstToSecond).Keys; }
    }

    IEnumerable<TFirst> IReadOnlyDictionary<TFirst, TSecond>.Keys
    {
        get { return ((IReadOnlyDictionary<TFirst, TSecond>)_firstToSecond).Keys; }
    }

    public ICollection<TSecond> Values
    {
        get { return _firstToSecond.Values; }
    }

    ICollection IDictionary.Values
    {
        get { return ((IDictionary)_firstToSecond).Values; }
    }

    IEnumerable<TSecond> IReadOnlyDictionary<TFirst, TSecond>.Values
    {
        get { return ((IReadOnlyDictionary<TFirst, TSecond>)_firstToSecond).Values; }
    }

    public IEnumerator<KeyValuePair<TFirst, TSecond>> GetEnumerator ()
    {
        return _firstToSecond.GetEnumerator();
    }

    IEnumerator IEnumerable.GetEnumerator ()
    {
        return GetEnumerator();
    }

    IDictionaryEnumerator IDictionary.GetEnumerator ()
    {
        return ((IDictionary)_firstToSecond).GetEnumerator();
    }

    public void Add (TFirst key, TSecond value)
    {
        _firstToSecond.Add(key, value);
        _secondToFirst.Add(value, key);
    }

    void IDictionary.Add (object key, object value)
    {
        ((IDictionary)_firstToSecond).Add(key, value);
        ((IDictionary)_secondToFirst).Add(value, key);
    }

    public void Add (KeyValuePair<TFirst, TSecond> item)
    {
        _firstToSecond.Add(item);
        _secondToFirst.Add(item.Reverse());
    }

    public bool ContainsKey (TFirst key)
    {
        return _firstToSecond.ContainsKey(key);
    }

    public bool Contains (KeyValuePair<TFirst, TSecond> item)
    {
        return _firstToSecond.Contains(item);
    }

    public bool TryGetValue (TFirst key, out TSecond value)
    {
        return _firstToSecond.TryGetValue(key, out value);
    }

    public bool Remove (TFirst key)
    {
        TSecond value;
        if (_firstToSecond.TryGetValue(key, out value)) {
            _firstToSecond.Remove(key);
            _secondToFirst.Remove(value);
            return true;
        }
        else
            return false;
    }

    void IDictionary.Remove (object key)
    {
        var firstToSecond = (IDictionary)_firstToSecond;
        if (!firstToSecond.Contains(key))
            return;
        var value = firstToSecond[key];
        firstToSecond.Remove(key);
        ((IDictionary)_secondToFirst).Remove(value);
    }

    public bool Remove (KeyValuePair<TFirst, TSecond> item)
    {
        return _firstToSecond.Remove(item);
    }

    public bool Contains (object key)
    {
        return ((IDictionary)_firstToSecond).Contains(key);
    }

    public void Clear ()
    {
        _firstToSecond.Clear();
        _secondToFirst.Clear();
    }

    public void CopyTo (KeyValuePair<TFirst, TSecond>[] array, int arrayIndex)
    {
        _firstToSecond.CopyTo(array, arrayIndex);
    }

    void ICollection.CopyTo (Array array, int index)
    {
        ((IDictionary)_firstToSecond).CopyTo(array, index);
    }

    [OnDeserialized]
    internal void OnDeserialized (StreamingContext context)
    {
        _secondToFirst.Clear();
        foreach (var item in _firstToSecond)
            _secondToFirst.Add(item.Value, item.Key);
    }

    private class ReverseDictionary : IDictionary<TSecond, TFirst>, IReadOnlyDictionary<TSecond, TFirst>, IDictionary
    {
        private readonly BiDictionary<TFirst, TSecond> _owner;

        public ReverseDictionary (BiDictionary<TFirst, TSecond> owner)
        {
            _owner = owner;
        }

        public int Count
        {
            get { return _owner._secondToFirst.Count; }
        }

        object ICollection.SyncRoot
        {
            get { return ((ICollection)_owner._secondToFirst).SyncRoot; }
        }

        bool ICollection.IsSynchronized
        {
            get { return ((ICollection)_owner._secondToFirst).IsSynchronized; }
        }

        bool IDictionary.IsFixedSize
        {
            get { return ((IDictionary)_owner._secondToFirst).IsFixedSize; }
        }

        public bool IsReadOnly
        {
            get { return _owner._secondToFirst.IsReadOnly || _owner._firstToSecond.IsReadOnly; }
        }

        public TFirst this [TSecond key]
        {
            get { return _owner._secondToFirst[key]; }
            set
            {
                _owner._secondToFirst[key] = value;
                _owner._firstToSecond[value] = key;
            }
        }

        object IDictionary.this [object key]
        {
            get { return ((IDictionary)_owner._secondToFirst)[key]; }
            set
            {
                ((IDictionary)_owner._secondToFirst)[key] = value;
                ((IDictionary)_owner._firstToSecond)[value] = key;
            }
        }

        public ICollection<TSecond> Keys
        {
            get { return _owner._secondToFirst.Keys; }
        }

        ICollection IDictionary.Keys
        {
            get { return ((IDictionary)_owner._secondToFirst).Keys; }
        }

        IEnumerable<TSecond> IReadOnlyDictionary<TSecond, TFirst>.Keys
        {
            get { return ((IReadOnlyDictionary<TSecond, TFirst>)_owner._secondToFirst).Keys; }
        }

        public ICollection<TFirst> Values
        {
            get { return _owner._secondToFirst.Values; }
        }

        ICollection IDictionary.Values
        {
            get { return ((IDictionary)_owner._secondToFirst).Values; }
        }

        IEnumerable<TFirst> IReadOnlyDictionary<TSecond, TFirst>.Values
        {
            get { return ((IReadOnlyDictionary<TSecond, TFirst>)_owner._secondToFirst).Values; }
        }

        public IEnumerator<KeyValuePair<TSecond, TFirst>> GetEnumerator ()
        {
            return _owner._secondToFirst.GetEnumerator();
        }

        IEnumerator IEnumerable.GetEnumerator ()
        {
            return GetEnumerator();
        }

        IDictionaryEnumerator IDictionary.GetEnumerator ()
        {
            return ((IDictionary)_owner._secondToFirst).GetEnumerator();
        }

        public void Add (TSecond key, TFirst value)
        {
            _owner._secondToFirst.Add(key, value);
            _owner._firstToSecond.Add(value, key);
        }

        void IDictionary.Add (object key, object value)
        {
            ((IDictionary)_owner._secondToFirst).Add(key, value);
            ((IDictionary)_owner._firstToSecond).Add(value, key);
        }

        public void Add (KeyValuePair<TSecond, TFirst> item)
        {
            _owner._secondToFirst.Add(item);
            _owner._firstToSecond.Add(item.Reverse());
        }

        public bool ContainsKey (TSecond key)
        {
            return _owner._secondToFirst.ContainsKey(key);
        }

        public bool Contains (KeyValuePair<TSecond, TFirst> item)
        {
            return _owner._secondToFirst.Contains(item);
        }

        public bool TryGetValue (TSecond key, out TFirst value)
        {
            return _owner._secondToFirst.TryGetValue(key, out value);
        }

        public bool Remove (TSecond key)
        {
            TFirst value;
            if (_owner._secondToFirst.TryGetValue(key, out value)) {
                _owner._secondToFirst.Remove(key);
                _owner._firstToSecond.Remove(value);
                return true;
            }
            else
                return false;
        }

        void IDictionary.Remove (object key)
        {
            var firstToSecond = (IDictionary)_owner._secondToFirst;
            if (!firstToSecond.Contains(key))
                return;
            var value = firstToSecond[key];
            firstToSecond.Remove(key);
            ((IDictionary)_owner._firstToSecond).Remove(value);
        }

        public bool Remove (KeyValuePair<TSecond, TFirst> item)
        {
            return _owner._secondToFirst.Remove(item);
        }

        public bool Contains (object key)
        {
            return ((IDictionary)_owner._secondToFirst).Contains(key);
        }

        public void Clear ()
        {
            _owner._secondToFirst.Clear();
            _owner._firstToSecond.Clear();
        }

        public void CopyTo (KeyValuePair<TSecond, TFirst>[] array, int arrayIndex)
        {
            _owner._secondToFirst.CopyTo(array, arrayIndex);
        }

        void ICollection.CopyTo (Array array, int index)
        {
            ((IDictionary)_owner._secondToFirst).CopyTo(array, index);
        }
    }
}

internal class DictionaryDebugView<TKey, TValue>
{
    private readonly IDictionary<TKey, TValue> _dictionary;

    [DebuggerBrowsable (DebuggerBrowsableState.RootHidden)]
    public KeyValuePair<TKey, TValue>[] Items
    {
        get
        {
            var array = new KeyValuePair<TKey, TValue>[_dictionary.Count];
            _dictionary.CopyTo(array, 0);
            return array;
        }
    }

    public DictionaryDebugView (IDictionary<TKey, TValue> dictionary)
    {
        if (dictionary == null)
            throw new ArgumentNullException("dictionary");
        _dictionary = dictionary;
    }
}

public static class KeyValuePairExts
{
    public static KeyValuePair<TValue, TKey> Reverse<TKey, TValue> (this KeyValuePair<TKey, TValue> @this)
    {
        return new KeyValuePair<TValue, TKey>(@this.Value, @this.Key);
    }
}


在这个答案中,您提到的问题也显示了一对一的实现。添加removebyfirst和removebysecond是很简单的——实现额外的接口等也是如此。


这和公认的答案是一样的,但我也提供了Update方法,而且总而言之,还提供了一些更丰富的方法:

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public class BiDictionary<TKey1, TKey2> : IEnumerable<Tuple<TKey1, TKey2>>
{
    Dictionary<TKey1, TKey2> _forwards;
    Dictionary<TKey2, TKey1> _reverses;

    public int Count
    {
        get
        {
            if (_forwards.Count != _reverses.Count)
                throw new Exception("somewhere logic went wrong and your data got corrupt");

            return _forwards.Count;
        }
    }

    public ICollection<TKey1> Key1s
    {
        get { return _forwards.Keys; }
    }

    public ICollection<TKey2> Key2s
    {
        get { return _reverses.Keys; }
    }

    public BiDictionary(IEqualityComparer<TKey1> comparer1 = null, IEqualityComparer<TKey2> comparer2 = null)
    {
        _forwards = new Dictionary<TKey1, TKey2>(comparer1);
        _reverses = new Dictionary<TKey2, TKey1>(comparer2);
    }



    public bool ContainsKey1(TKey1 key)
    {
        return ContainsKey(key, _forwards);
    }

    private static bool ContainsKey<S, T>(S key, Dictionary<S, T> dict)
    {
        return dict.ContainsKey(key);
    }

    public bool ContainsKey2(TKey2 key)
    {
        return ContainsKey(key, _reverses);
    }

    public TKey2 GetValueByKey1(TKey1 key)
    {
        return GetValueByKey(key, _forwards);
    }

    private static T GetValueByKey<S, T>(S key, Dictionary<S, T> dict)
    {
        return dict[key];
    }

    public TKey1 GetValueByKey2(TKey2 key)
    {
        return GetValueByKey(key, _reverses);
    }

    public bool TryGetValueByKey1(TKey1 key, out TKey2 value)
    {
        return TryGetValue(key, _forwards, out value);
    }

    private static bool TryGetValue<S, T>(S key, Dictionary<S, T> dict, out T value)
    {
        return dict.TryGetValue(key, out value);
    }

    public bool TryGetValueByKey2(TKey2 key, out TKey1 value)
    {
        return TryGetValue(key, _reverses, out value);
    }

    public bool Add(TKey1 key1, TKey2 key2)
    {
        if (ContainsKey1(key1) || ContainsKey2(key2))   // very important
            return false;

        AddOrUpdate(key1, key2);
        return true;
    }

    public void AddOrUpdateByKey1(TKey1 key1, TKey2 key2)
    {
        if (!UpdateByKey1(key1, key2))
            AddOrUpdate(key1, key2);
    }

    // dont make this public; a dangerous method used cautiously in this class
    private void AddOrUpdate(TKey1 key1, TKey2 key2)
    {
        _forwards[key1] = key2;
        _reverses[key2] = key1;
    }

    public void AddOrUpdateKeyByKey2(TKey2 key2, TKey1 key1)
    {
        if (!UpdateByKey2(key2, key1))
            AddOrUpdate(key1, key2);
    }

    public bool UpdateKey1(TKey1 oldKey, TKey1 newKey)
    {
        return UpdateKey(oldKey, _forwards, newKey, (key1, key2) => AddOrUpdate(key1, key2));
    }

    private static bool UpdateKey<S, T>(S oldKey, Dictionary<S, T> dict, S newKey, Action<S, T> updater)
    {
        T otherKey;
        if (!TryGetValue(oldKey, dict, out otherKey) || ContainsKey(newKey, dict))
            return false;

        Remove(oldKey, dict);
        updater(newKey, otherKey);
        return true;
    }

    public bool UpdateKey2(TKey2 oldKey, TKey2 newKey)
    {
        return UpdateKey(oldKey, _reverses, newKey, (key1, key2) => AddOrUpdate(key2, key1));
    }

    public bool UpdateByKey1(TKey1 key1, TKey2 key2)
    {
        return UpdateByKey(key1, _forwards, _reverses, key2, (k1, k2) => AddOrUpdate(k1, k2));
    }

    private static bool UpdateByKey<S, T>(S key1, Dictionary<S, T> forwards, Dictionary<T, S> reverses, T key2,
                                          Action<S, T> updater)
    {
        T otherKey;
        if (!TryGetValue(key1, forwards, out otherKey) || ContainsKey(key2, reverses))
            return false;

        if (!Remove(otherKey, reverses))
            throw new Exception("somewhere logic went wrong and your data got corrupt");

        updater(key1, key2);
        return true;
    }

    public bool UpdateByKey2(TKey2 key2, TKey1 key1)
    {
        return UpdateByKey(key2, _reverses, _forwards, key1, (k1, k2) => AddOrUpdate(k2, k1));
    }

    public bool RemoveByKey1(TKey1 key)
    {
        return RemoveByKey(key, _forwards, _reverses);
    }

    private static bool RemoveByKey<S, T>(S key, Dictionary<S, T> keyDict, Dictionary<T, S> valueDict)
    {
        T otherKey;
        if (!TryGetValue(key, keyDict, out otherKey))
            return false;

        if (!Remove(key, keyDict) || !Remove(otherKey, valueDict))
            throw new Exception("somewhere logic went wrong and your data got corrupt");

        return true;
    }

    private static bool Remove<S, T>(S key, Dictionary<S, T> dict)
    {
        return dict.Remove(key);
    }

    public bool RemoveByKey2(TKey2 key)
    {
        return RemoveByKey(key, _reverses, _forwards);
    }

    public void Clear()
    {
        _forwards.Clear();
        _reverses.Clear();
    }

    public IEnumerator<Tuple<TKey1, TKey2>> GetEnumerator()
    {
        if (_forwards.Count != _reverses.Count)
            throw new Exception("somewhere logic went wrong and your data got corrupt");

        foreach (var item in _forwards)
            yield return Tuple.Create(item.Key, item.Value);
    }

    IEnumerator IEnumerable.GetEnumerator()
    {
        return GetEnumerator();
    }
}

和我这里的答案相似

需要注意的几点:

  • 我只执行了IEnumerable<>。我认为ICollection<>在这里没有意义,因为对于这个特殊的收集结构,方法名可能都有很大的不同。由你来决定应该在IEnumerable<>内做什么。所以现在您也有了集合初始值设定项语法,比如

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    var p = new BiDictionary<int, string> { 1,"a" }, { 2,"b" } };
  • 我曾尝试在这里和那里抛出一些奇怪的异常——只是为了数据完整性。只是为了更安全一点,这样你就知道我的代码是否有错误。

  • 性能:您可以使用Keys中的任何一个查找Value,这意味着GetContains方法只需要1个查找(o(1))。Add需要2次查找和2次添加。Update需要1次查找和2次添加。Remove进行3次查找。均与公认答案相似。


  • 对已接受答案的另一个扩展。它实现IEnumerable,因此可以将foreach与它一起使用。我知道IEnumerable实现有更多的答案,但是这个实现使用结构,所以它是垃圾收集器友好的。这在Unity引擎中尤其有用(使用探查器进行检查)。

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    /// <summary>
    /// This is a dictionary guaranteed to have only one of each value and key.
    /// It may be searched either by TFirst or by TSecond, giving a unique answer because it is 1 to 1.
    /// It implements garbage-collector-friendly IEnumerable.
    /// </summary>
    /// <typeparam name="TFirst">The type of the"key"</typeparam>
    /// <typeparam name="TSecond">The type of the"value"</typeparam>
    public class BiDictionary<TFirst, TSecond> : IEnumerable<BiDictionary<TFirst, TSecond>.Pair>
    {


        public struct Pair
        {
            public TFirst  First;
            public TSecond Second;
        }


        public struct Enumerator : IEnumerator<Pair>, IEnumerator
        {

            public Enumerator(Dictionary<TFirst, TSecond>.Enumerator dictEnumerator)
            {
                _dictEnumerator = dictEnumerator;
            }

            public Pair Current
            {
                get
                {
                    Pair pair;
                    pair.First = _dictEnumerator.Current.Key;
                    pair.Second = _dictEnumerator.Current.Value;
                    return pair;
                }
            }

            object IEnumerator.Current
            {
                get
                {
                    return Current;
                }
            }

            public void Dispose()
            {
                _dictEnumerator.Dispose();
            }

            public bool MoveNext()
            {
                return _dictEnumerator.MoveNext();
            }

            public void Reset()
            {
                throw new NotSupportedException();
            }

            private Dictionary<TFirst, TSecond>.Enumerator _dictEnumerator;

        }

        #region Exception throwing methods

        /// <summary>
        /// Tries to add the pair to the dictionary.
        /// Throws an exception if either element is already in the dictionary
        /// </summary>
        /// <param name="first"></param>
        /// <param name="second"></param>
        public void Add(TFirst first, TSecond second)
        {
            if (_firstToSecond.ContainsKey(first) || _secondToFirst.ContainsKey(second))
                throw new ArgumentException("Duplicate first or second");

            _firstToSecond.Add(first, second);
            _secondToFirst.Add(second, first);
        }

        /// <summary>
        /// Find the TSecond corresponding to the TFirst first
        /// Throws an exception if first is not in the dictionary.
        /// </summary>
        /// <param name="first">the key to search for</param>
        /// <returns>the value corresponding to first</returns>
        public TSecond GetByFirst(TFirst first)
        {
            TSecond second;
            if (!_firstToSecond.TryGetValue(first, out second))
                throw new ArgumentException("first");

            return second;
        }

        /// <summary>
        /// Find the TFirst corresponing to the Second second.
        /// Throws an exception if second is not in the dictionary.
        /// </summary>
        /// <param name="second">the key to search for</param>
        /// <returns>the value corresponding to second</returns>
        public TFirst GetBySecond(TSecond second)
        {
            TFirst first;
            if (!_secondToFirst.TryGetValue(second, out first))
                throw new ArgumentException("second");

            return first;
        }


        /// <summary>
        /// Remove the record containing first.
        /// If first is not in the dictionary, throws an Exception.
        /// </summary>
        /// <param name="first">the key of the record to delete</param>
        public void RemoveByFirst(TFirst first)
        {
            TSecond second;
            if (!_firstToSecond.TryGetValue(first, out second))
                throw new ArgumentException("first");

            _firstToSecond.Remove(first);
            _secondToFirst.Remove(second);
        }

        /// <summary>
        /// Remove the record containing second.
        /// If second is not in the dictionary, throws an Exception.
        /// </summary>
        /// <param name="second">the key of the record to delete</param>
        public void RemoveBySecond(TSecond second)
        {
            TFirst first;
            if (!_secondToFirst.TryGetValue(second, out first))
                throw new ArgumentException("second");

            _secondToFirst.Remove(second);
            _firstToSecond.Remove(first);
        }

        #endregion

        #region Try methods

        /// <summary>
        /// Tries to add the pair to the dictionary.
        /// Returns false if either element is already in the dictionary        
        /// </summary>
        /// <param name="first"></param>
        /// <param name="second"></param>
        /// <returns>true if successfully added, false if either element are already in the dictionary</returns>
        public bool TryAdd(TFirst first, TSecond second)
        {
            if (_firstToSecond.ContainsKey(first) || _secondToFirst.ContainsKey(second))
                return false;

            _firstToSecond.Add(first, second);
            _secondToFirst.Add(second, first);
            return true;
        }


        /// <summary>
        /// Find the TSecond corresponding to the TFirst first.
        /// Returns false if first is not in the dictionary.
        /// </summary>
        /// <param name="first">the key to search for</param>
        /// <param name="second">the corresponding value</param>
        /// <returns>true if first is in the dictionary, false otherwise</returns>
        public bool TryGetByFirst(TFirst first, out TSecond second)
        {
            return _firstToSecond.TryGetValue(first, out second);
        }

        /// <summary>
        /// Find the TFirst corresponding to the TSecond second.
        /// Returns false if second is not in the dictionary.
        /// </summary>
        /// <param name="second">the key to search for</param>
        /// <param name="first">the corresponding value</param>
        /// <returns>true if second is in the dictionary, false otherwise</returns>
        public bool TryGetBySecond(TSecond second, out TFirst first)
        {
            return _secondToFirst.TryGetValue(second, out first);
        }

        /// <summary>
        /// Remove the record containing first, if there is one.
        /// </summary>
        /// <param name="first"></param>
        /// <returns> If first is not in the dictionary, returns false, otherwise true</returns>
        public bool TryRemoveByFirst(TFirst first)
        {
            TSecond second;
            if (!_firstToSecond.TryGetValue(first, out second))
                return false;

            _firstToSecond.Remove(first);
            _secondToFirst.Remove(second);
            return true;
        }

        /// <summary>
        /// Remove the record containing second, if there is one.
        /// </summary>
        /// <param name="second"></param>
        /// <returns> If second is not in the dictionary, returns false, otherwise true</returns>
        public bool TryRemoveBySecond(TSecond second)
        {
            TFirst first;
            if (!_secondToFirst.TryGetValue(second, out first))
                return false;

            _secondToFirst.Remove(second);
            _firstToSecond.Remove(first);
            return true;
        }

        #endregion        

        /// <summary>
        /// The number of pairs stored in the dictionary
        /// </summary>
        public Int32 Count
        {
            get { return _firstToSecond.Count; }
        }

        /// <summary>
        /// Removes all items from the dictionary.
        /// </summary>
        public void Clear()
        {
            _firstToSecond.Clear();
            _secondToFirst.Clear();
        }


        public Enumerator GetEnumerator()
        {
            //enumerator.Reset(firstToSecond.GetEnumerator());
            return new Enumerator(_firstToSecond.GetEnumerator());
        }

        IEnumerator<Pair> IEnumerable<Pair>.GetEnumerator()
        {
            return GetEnumerator();
        }

        IEnumerator IEnumerable.GetEnumerator()
        {
            return GetEnumerator();
        }



        private Dictionary<TFirst, TSecond> _firstToSecond  = new Dictionary<TFirst, TSecond>();
        private Dictionary<TSecond, TFirst> _secondToFirst  = new Dictionary<TSecond, TFirst>();

    }


    我使用c5集合类创建了这样一个类。

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    public class Mapper<K,T> : IEnumerable<T>

    {
        C5.TreeDictionary<K,T> KToTMap = new TreeDictionary<K,T>();
        C5.HashDictionary<T,K> TToKMap = new HashDictionary<T,K>();


        /// <summary>
        /// Initializes a new instance of the Mapper class.
        /// </summary>
        public Mapper()
        {
            KToTMap = new TreeDictionary<K,T>();
            TToKMap = new HashDictionary<T,K>();
        }


        public void Add(K key, T value)
        {
            KToTMap.Add(key, value);
            TToKMap.Add(value, key);
        }

        public bool ContainsKey(K key)
        {
            return KToTMap.Contains(key);
        }

        public int Count
        {
            get { return KToTMap.Count; }
        }


        public K this[T obj]
        {
            get
            {
                return TToKMap[obj];
            }
        }

        public T this[K obj]
        {
            get
            {
                return KToTMap[obj];
            }
        }

        public IEnumerator<T> GetEnumerator()
        {
            return KToTMap.Values.GetEnumerator();
        }

        System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
        {
            return KToTMap.Values.GetEnumerator();
        }
    }


    有点晚了,但这里有一个我前一段时间写的实现。它处理一些有趣的边缘情况,例如当键重写相等检查以执行部分相等时。这导致主字典存储A => 1,而反向存储1 => A'

    您可以通过Inverse属性访问反向字典。

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    var map = new BidirectionalDictionary<int, int>();
    map.Add(1, 2);
    var result = map.Inverse[2]; // result is 1
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    //
    // BidirectionalDictionary.cs
    //
    // Author:
    //   Chris Chilvers <[email protected]>
    //
    // Copyright (c) 2009 Chris Chilvers
    //
    // Permission is hereby granted, free of charge, to any person obtaining
    // a copy of this software and associated documentation files (the
    //"Software"), to deal in the Software without restriction, including
    // without limitation the rights to use, copy, modify, merge, publish,
    // distribute, sublicense, and/or sell copies of the Software, and to
    // permit persons to whom the Software is furnished to do so, subject to
    // the following conditions:
    //
    // The above copyright notice and this permission notice shall be
    // included in all copies or substantial portions of the Software.
    //
    // THE SOFTWARE IS PROVIDED"AS IS", WITHOUT WARRANTY OF ANY KIND,
    // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
    // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
    // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
    // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
    // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
    // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
    //

    using System;
    using System.Collections;
    using System.Collections.Generic;

    namespace Cadenza.Collections
    {
        public class BidirectionalDictionary<TKey, TValue> : IDictionary<TKey, TValue>
        {
            private readonly IEqualityComparer<TKey> keyComparer;
            private readonly IEqualityComparer<TValue> valueComparer;
            private readonly Dictionary<TKey, TValue> keysToValues;
            private readonly Dictionary<TValue, TKey> valuesToKeys;
            private readonly BidirectionalDictionary<TValue, TKey> inverse;


            public BidirectionalDictionary () : this (10, null, null) {}

            public BidirectionalDictionary (int capacity) : this (capacity, null, null) {}

            public BidirectionalDictionary (IEqualityComparer<TKey> keyComparer, IEqualityComparer<TValue> valueComparer)
                : this (10, keyComparer, valueComparer)
            {
            }

            public BidirectionalDictionary (int capacity, IEqualityComparer<TKey> keyComparer, IEqualityComparer<TValue> valueComparer)
            {
                if (capacity < 0)
                    throw new ArgumentOutOfRangeException ("capacity", capacity,"capacity cannot be less than 0");

                this.keyComparer = keyComparer ?? EqualityComparer<TKey>.Default;
                this.valueComparer = valueComparer ?? EqualityComparer<TValue>.Default;

                keysToValues = new Dictionary<TKey, TValue> (capacity, this.keyComparer);
                valuesToKeys = new Dictionary<TValue, TKey> (capacity, this.valueComparer);

                inverse = new BidirectionalDictionary<TValue, TKey> (this);
            }

            private BidirectionalDictionary (BidirectionalDictionary<TValue, TKey> inverse)
            {
                this.inverse = inverse;
                keyComparer = inverse.valueComparer;
                valueComparer = inverse.keyComparer;
                valuesToKeys = inverse.keysToValues;
                keysToValues = inverse.valuesToKeys;
            }


            public BidirectionalDictionary<TValue, TKey> Inverse {
                get { return inverse; }
            }


            public ICollection<TKey> Keys {
                get { return keysToValues.Keys; }
            }

            public ICollection<TValue> Values {
                get { return keysToValues.Values; }
            }

            public IEnumerator<KeyValuePair<TKey, TValue>> GetEnumerator ()
            {
                return keysToValues.GetEnumerator ();
            }

            IEnumerator IEnumerable.GetEnumerator ()
            {
                return GetEnumerator ();
            }

            void ICollection<KeyValuePair<TKey, TValue>>.CopyTo (KeyValuePair<TKey, TValue>[] array, int arrayIndex)
            {
                ((ICollection<KeyValuePair<TKey, TValue>>) keysToValues).CopyTo (array, arrayIndex);
            }


            public bool ContainsKey (TKey key)
            {
                if (key == null)
                    throw new ArgumentNullException ("key");
                return keysToValues.ContainsKey (key);
            }

            public bool ContainsValue (TValue value)
            {
                if (value == null)
                    throw new ArgumentNullException ("value");
                return valuesToKeys.ContainsKey (value);
            }

            bool ICollection<KeyValuePair<TKey, TValue>>.Contains (KeyValuePair<TKey, TValue> item)
            {
                return ((ICollection<KeyValuePair<TKey, TValue>>) keysToValues).Contains (item);
            }

            public bool TryGetKey (TValue value, out TKey key)
            {
                if (value == null)
                    throw new ArgumentNullException ("value");
                return valuesToKeys.TryGetValue (value, out key);
            }

            public bool TryGetValue (TKey key, out TValue value)
            {
                if (key == null)
                    throw new ArgumentNullException ("key");
                return keysToValues.TryGetValue (key, out value);
            }

            public TValue this[TKey key] {
                get { return keysToValues [key]; }
                set {
                    if (key == null)
                        throw new ArgumentNullException ("key");
                    if (value == null)
                        throw new ArgumentNullException ("value");

                    //foo[5] ="bar"; foo[6] ="bar"; should not be valid
                    //as it would have to remove foo[5], which is unexpected.
                    if (ValueBelongsToOtherKey (key, value))
                        throw new ArgumentException ("Value already exists","value");

                    TValue oldValue;
                    if (keysToValues.TryGetValue (key, out oldValue)) {
                        // Use the current key for this value to stay consistent
                        // with Dictionary<TKey, TValue> which does not alter
                        // the key if it exists.
                        TKey oldKey = valuesToKeys [oldValue];

                        keysToValues [oldKey] = value;
                        valuesToKeys.Remove (oldValue);
                        valuesToKeys [value] = oldKey;
                    } else {
                        keysToValues [key] = value;
                        valuesToKeys [value] = key;
                    }
                }
            }

            public int Count {
                get { return keysToValues.Count; }
            }

            bool ICollection<KeyValuePair<TKey, TValue>>.IsReadOnly {
                get { return false; }
            }


            public void Add (TKey key, TValue value)
            {
                if (key == null)
                    throw new ArgumentNullException ("key");
                if (value == null)
                    throw new ArgumentNullException ("value");

                if (keysToValues.ContainsKey (key))
                    throw new ArgumentException ("Key already exists","key");
                if (valuesToKeys.ContainsKey (value))
                    throw new ArgumentException ("Value already exists","value");

                keysToValues.Add (key, value);
                valuesToKeys.Add (value, key);
            }

            public void Replace (TKey key, TValue value)
            {
                if (key == null)
                    throw new ArgumentNullException ("key");
                if (value == null)
                    throw new ArgumentNullException ("value");

                // replaces a key value pair, if the key or value already exists those mappings will be replaced.
                // e.g. you have; a -> b, b -> a; c -> d, d -> c
                // you add the mapping; a -> d, d -> a
                // this will remove both of the original mappings
                Remove (key);
                inverse.Remove (value);
                Add (key, value);
            }

            void ICollection<KeyValuePair<TKey, TValue>>.Add (KeyValuePair<TKey, TValue> item)
            {
                Add (item.Key, item.Value);
            }

            public bool Remove (TKey key)
            {
                if (key == null)
                    throw new ArgumentNullException ("key");

                TValue value;
                if (keysToValues.TryGetValue (key, out value)) {
                    keysToValues.Remove (key);
                    valuesToKeys.Remove (value);
                    return true;
                }
                else {
                    return false;
                }
            }

            bool ICollection<KeyValuePair<TKey, TValue>>.Remove (KeyValuePair<TKey, TValue> item)
            {
                bool removed = ((ICollection<KeyValuePair<TKey, TValue>>) keysToValues).Remove (item);
                if (removed)
                    valuesToKeys.Remove (item.Value);
                return removed;
            }

            public void Clear ()
            {
                keysToValues.Clear ();
                valuesToKeys.Clear ();
            }


            private bool ValueBelongsToOtherKey (TKey key, TValue value)
            {
                TKey otherKey;
                if (valuesToKeys.TryGetValue (value, out otherKey))
                    // if the keys are not equal the value belongs to another key
                    return !keyComparer.Equals (key, otherKey);
                else
                    // value doesn't exist in map, thus it cannot belong to another key
                    return false;
            }
        }
    }

    GitHub上的原始源和测试。