MutableLookup

A .NET Standard 2.0 library for mutable ILookup collections.

Defines an interface IMutableLookup for defining mutable ILookup containers:

public interface IMutableLookup<TKey, TElement> : ILookup<TKey, TElement>
{
    void Add(TKey key, TElement value);
    bool Remove(TKey key);
    bool Remove(TKey key, TElement value);
    void Clear();
    bool TryGetValues(TKey key, out IEnumerable<TElement> values);
}

Comes with a few predefined types that utilise .NET's own generic collection types:

• ListLookup<TKey, TElement> equivalent to Dictionary<TKey, List<TElement>>
• LinkedListLookup<TKey, TElement> equivalent to Dictionary<TKey, LinkedList<TElement>>
• HashSetLookup<TKey, TElement> equivalent to Dictionary<TKey, HashSet<TElement>>

Each type has its own advantages and disadvantages based on use case requirements.

Installation

Install MutableLookup through NuGet:

NuGet install MutableLookup

NuGet package page: https://www.nuget.org/packages/MutableLookup

Implementing your own IMutableLookup

The library comes with the MutableLookup abstract class which allows trivial definition of a new IMutableLookup. Given a type MyCollection<TElement> that implements ICollection<TElement>, you can define a new IMutableLookup type like this:

public sealed class MyCollectionLookup<TKey, TElement>
    : MutableLookup<TKey, TElement, MyCollection<TElement>> { }

If your collection does not implement a constant time .Count property, you should override the bool IsContainerEmpty(TContainer container) method to efficiently see if the container is empty.