Gapotchenko.FX.Collections 2022.1.4

Overview

The module was started by borrowing an implementation of ConcurrentHashSet<T> from Mr. Bar Arnon.

Other than that, the module provides polyfills for missing functionality in .NET.

ConcurrentHashSet<T>

ConcurrentHashSet<T> provided by Gapotchenko.FX.Collections is a thread-safe implementation of HashSet<T>.

AssociativeArray<TKey, TValue>

AssociativeArray<TKey, TValue> provided by Gapotchenko.FX.Collections is a drop-in replacement for Dictionary<TKey, TValue> that can handle null keys.

In contrast, stock Dictionary<TKey, TValue> cannot work with null keys and throws an exception whenever a null key is encountered. Due to such an artificial narrowing of the key space, it becomes hardly possible to solve some kinds of tasks with Dictionary<TKey, TValue>.

AssociativeArray<TKey, TValue> resolves that by supporting a full space of keys without opinionated exclusions.

AddRange<T>(IEnumerable<T>) for Collections

AddRange is a highly demanded operation that allows to add a sequence of elements to the end of a collection. Like this:

using Gapotchenko.FX.Collections.Generic;

var collection = new Collection<int>();
…
collection.AddRange(numbers.Where(x => x % 2 == 0)); // add even numbers

IsNullOrEmpty() for Containers

System.String class provides a convenient IsNullOrEmpty primitive.

Gapotchenko.FX.Collections extends availability of that primitive by providing IsNullOrEmpty() extension method for other container types. Here is an example:

using Gapotchenko.FX.Collections.Generic;

class Method
{
    List<Argument> m_Arguments;

    public bool HasArguments => !m_Arguments.IsNullOrEmpty();

    …
}

The use of an extension method for a null check may look controversial at first, but since the method starts with IsNull… prefix, it immediately communicates its purpose and function. Other benefits include automatic type inference and semantic locality.

Polyfills

KeyValuePair Polyfill

.NET provides a versatile KeyValuePair<TKey, TValue> struct and suggests a default way for its instantiation:

new KeyValuePair<TKey, TValue>(key, value)

Which is, well, not handy as it often comes to this:

new KeyValuePair<BindingManagerDataErrorEventHandler, ICom2PropertyPageDisplayService>(key, value)

Gapotchenko.FX.Collections provides a better way to instantiate a KeyValuePair<TKey, TValue> struct:

using Gapotchenko.FX.Collections.Generic;

KeyValuePair.Create(key, value)

It leverages the automatic type inference provided by some .NET languages like C#.

PriorityQueue polyfill

PriorityQueue<TElement, TPriority> provided by Gapotchenko.FX.Collections module is an implementation of the prioritized queue introduced since .NET 6. The polyfill makes it available to all supported .NET versions.

Deconstruction

Gapotchenko.FX.Collections module comes with a function for KeyValuePair<TKey, TValue> deconstruction, so you can write this:

using Gapotchenko.FX.Collections.Generic;

void ProcessMap(IDictionary<string, int> map)
{
    foreach (var (key, value) in map)
    {
        …
    }
}

instead of a more verbose variant:

void ProcessMap(IDictionary<string, int> map)
{
    foreach (var i in map)
    {
        var key = i.Key;
        var value = i.Value;
        …
    }
}

A little detail, but sometimes it matters a lot when you are amid the heat of the code.