Get all subsets of a collection

Question

I am trying to create a method that will return all subsets of a set.

For example if I have the collection 10,20,30 I will like to get the following ou

Answer 1

Get all subsets of a collection of a specific subsetlength:

    public static IEnumerable> GetPermutations(IEnumerable list, int length) where T : IComparable
    {
        if (length == 1) return list.Select(t => new T[] { t });
        return GetPermutations(list, length - 1).SelectMany(t => list.Where(e => t.All(g => g.CompareTo(e) != 0)), (t1, t2) => t1.Concat(new T[] { t2 }));
    }

    public static IEnumerable> GetOrderedSubSets(IEnumerable list, int length) where T : IComparable
    {
        if (length == 1) return list.Select(t => new T[] { t });
        return GetOrderedSubSets(list, length - 1).SelectMany(t => list.Where(e => t.All(g => g.CompareTo(e) == -1)), (t1, t2) => t1.Concat(new T[] { t2 }));
    }

Testcode:

        List set = new List { 1, 2, 3 };
        foreach (var x in GetPermutations(set, 3))
        {
            Console.WriteLine(string.Join(", ", x));
        }
        Console.WriteLine();
        foreach (var x in GetPermutations(set, 2))
        {
            Console.WriteLine(string.Join(", ", x));
        }
        Console.WriteLine();
        foreach (var x in GetOrderedSubSets(set, 2))
        {
            Console.WriteLine(string.Join(", ", x));
        }

Test results:

1, 2, 3
1, 3, 2
2, 1, 3
2, 3, 1
3, 1, 2
3, 2, 1

1, 2
1, 3
2, 1
2, 3
3, 1
3, 2

1, 2
1, 3
2, 3