C#•13mo ago

Is there some standard KeyValue collection allowing adding by value and retrive by key, not dict?

Something like this

public interface IKeyd<TKey> where TKey: IEquatable<TKey>
{
    public TKey Key { get; }
}
public class KeyValueCollection<TKey, TValue> where TValue: IKeyd<TKey> where TKey: IEquatable<TKey>
{
    private Dictionary<TKey, TValue> _keyValues = new();
    public void Add(TValue value)
    {
        _keyValues.Add(value.Key, value);
    }
    public bool TryGetValue(TKey key, out TValue value)
    {
        return _keyValues.TryGetValue(key, out value);
    }
    public bool Contains(TValue value)
    {
        return _keyValues.ContainsKey(value.Key);
    }
    public bool Contains(TKey key)
    {
        return _keyValues.ContainsKey(key);
    }
    public bool Remove(TKey key)
    {
        return _keyValues.Remove(key);
    }
    public bool Remove(TValue value)
    {
        return _keyValues.Remove(value.Key);
    }
}

public interface IKeyd<TKey> where TKey: IEquatable<TKey>
{
    public TKey Key { get; }
}
public class KeyValueCollection<TKey, TValue> where TValue: IKeyd<TKey> where TKey: IEquatable<TKey>
{
    private Dictionary<TKey, TValue> _keyValues = new();
    public void Add(TValue value)
    {
        _keyValues.Add(value.Key, value);
    }
    public bool TryGetValue(TKey key, out TValue value)
    {
        return _keyValues.TryGetValue(key, out value);
    }
    public bool Contains(TValue value)
    {
        return _keyValues.ContainsKey(value.Key);
    }
    public bool Contains(TKey key)
    {
        return _keyValues.ContainsKey(key);
    }
    public bool Remove(TKey key)
    {
        return _keyValues.Remove(key);
    }
    public bool Remove(TValue value)
    {
        return _keyValues.Remove(value.Key);
    }
}

6 Replies

mtreit•13mo ago

I don't see what that adds over just using a dictionary

RumTeryOP•13mo ago

Dictionaries Contains(TValue value) is O(n), moreover it allows to specify one object for both key and value

Jimmacle•13mo ago

that's why you don't search a dictionary by value, that's not what it's designed to be good at

mtreit•13mo ago

I mean, in your example it's still looking by key not by value So I don't understand the ask.

Jimmacle•13mo ago

the only real difference here is your collection duplicates the value's key in the value itself

mtreit•13mo ago

Right, which is just a regular dictionary except there is some limitation requiring the value has a key attached to it. If you want fast lookup by both keys and by values, use two dictionaries. One for regular lookup, one for reverse lookup.

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Is there some standard KeyValue collection allowing adding by value and retrive by key, not dict?