Convert a lambda expression to an IEqualityComparer<>

LambdaComparer.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Shared;

/// <summary>
/// Convert a lambda expression to an IEqualityComparer<>.
/// </summary>
/// <remarks>
/// Can also make an extension to hide the use of this class in a LINQ method:
/// 
/// public static class MyExtensions
/// {
///     public static IEnumerable<TSource> Except<TSource>(this IEnumerable<TSource> first, 
///																			IEnumerable<TSource> second,
///																			Func<TSource, TSource, bool> comparer)
///     {
///         return first.Except(second, new LambdaComparer<TSource>(comparer));
///     }
/// }
/// </remarks>
/// <see cref="http://brendan.enrick.com/post/LINQ-Your-Collections-with-IEqualityComparer-and-Lambda-Expressions" />
/// <example>
/// List<MyObject> x = myCollection.Except(otherCollection, new LambdaComparer<MyObject>((x, y) => x.Id == y.Id)).ToList();
/// </example>
/// <typeparam name="T"></typeparam>
internal class LambdaComparer<T> : IEqualityComparer<T>
{
	private readonly Func<T, T, bool> _lambdaComparer; // Equals()
	private readonly Func<T, int> _lambdaHash;         // GetHashCode()

	// Use default GetHashCode()
	internal LambdaComparer(Func<T, T, bool> lambdaComparer) :
		 this(lambdaComparer, obj => obj?.GetHashCode() ?? 0)
	{
	}

	internal LambdaComparer(Func<T, T, bool> lambdaComparer, Func<T, int> lambdaHash)
	{
		_lambdaComparer = lambdaComparer ?? throw new ArgumentNullException(nameof(lambdaComparer));
		_lambdaHash = lambdaHash ?? throw new ArgumentNullException(nameof(lambdaHash));
	}

	public bool Equals(T x, T y)
	{
		if (x is null)
		{
			return (y is null);
		}

		if (y is null)
		{
			return false;
		}

		return _lambdaComparer(x, y);
	}

	public int GetHashCode(T obj)
	{
		return _lambdaHash(obj);
	}
}