Bidirectional 1 to 1 Dictionary in C#
I am looking for a generic, bidirectional 1 to 1 Dictionary class in C# (2), ie. a BiDictionaryOneToOne<T, S> which is guaranteed to only contain one of each value and key (up to RefEquals anyway), and which can be searched using either key or value. Anyone know of one, or should I just implement it myself? I can't believe that I'm the first person to need this...
There is a BiDictionary in the answers to this question, but it is not for unique elements (and also does not implement RemoveByFirst(T t) or RemoveBySecond(S s)).
Thanks!
好的，这里是我的尝试（建立在Jon的基础上 - 谢谢），在这里归档并开放改进：
/// <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();
}
}
A more complete implementation of bidirectional dictionary:
Dictionary<TKey,TValue> (except infrastructure interfaces): IDictionary<TKey, TValue> IReadOnlyDictionary<TKey, TValue> IDictionary ICollection<KeyValuePair<TKey, TValue>> (this one and below are the base interfaces of the ones above) ICollection IReadOnlyCollection<KeyValuePair<TKey, TValue>> IEnumerable<KeyValuePair<TKey, TValue>> IEnumerable SerializableAttribute . DebuggerDisplayAttribute (with Count info) and DebuggerTypeProxyAttribute (for displaying key-value pairs in watches). IDictionary<TValue, TKey> Reverse property and also implements all interfaces mentioned above. All operations on either dictionaries modify both. Usage:
var dic = new BiDictionary<int, string>();
dic.Add(1, "1");
dic[2] = "2";
dic.Reverse.Add("3", 3);
dic.Reverse["4"] = 4;
dic.Clear();
Code is available in my private framework on GitHub: BiDictionary(TFirst,TSecond).cs (permalink, search).
Copy:
[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);
}
}
The question you refer to also shows a one-to-one implementation in this answer. Adding RemoveByFirst and RemoveBySecond would be trivial - as would implementing extra interfaces etc.
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