LINQ Full Outer Join extension

IEnumerableExtensions.cs

using System;
using System.Collections.Generic;
using System.Linq;

namespace System.Collections.Generic
{
    public static class IEnumerableExtensions
    {
        public static IEnumerable<(T1 Left, T2 Right)> FullOuterJoin<T1, T2>(this IEnumerable<T1> left, IEnumerable<T2> right, Func<T1, T2, bool> match)
        {
            var leftResults = from l in left
                              from r in right.Where(r => match(l, r)).DefaultIfEmpty()
                       select (Left: l, Right: r);

            var rightResults = from r in right
                               from l in left.Where(l => match(l, r)).DefaultIfEmpty()
                        select (Left: l, Right: r);

            return leftResults.Concat(rightResults).Distinct();
        }
    }
}