A C# IList extension method that returns all combinations of the content of the list. See related question on StackOverflow: https://stackoverflow.com/questions/7802822/all-possible-combinations-of-a-list-of-values/40417765#40417765

AllCombinations.cs

using System;
using System.Collections.Generic;

public static class ListExtensions
{
    public static IEnumerable<List<TInput>> AllCombinations<TInput>(this IList<TInput> list)
        => list.AllCombinations(() => new List<TInput>(), (list, item) => list.Add(item));

    public static IEnumerable<TCombinationContainer> AllCombinations<TInput, TCombinationContainer>(
        this IList<TInput> list,
        Func<TCombinationContainer> combinationContainerFactory,
        Action<TCombinationContainer, TInput> combinationAggregator)
    {
        if (list is null) throw new ArgumentNullException(nameof(list));

        int comboCount = (int)Math.Pow(2, list.Count) - 1;
        for (int i = 1; i <= comboCount; i++)
        {
            var combiContainer = combinationContainerFactory();

            for (int j = 0; j < list.Count; j++)
            {
                if ((i >> j) % 2 != 0)
                {
                    combinationAggregator(combiContainer, list[j]);
                }
            }
            yield return combiContainer;
        }
    }
}