Generate word combination array in c#

Question

I have a string such as \"big bad dog\", how can I get an string[] array which includes all the possible word/phrase combinations?

So, I would like to return \"big\"

Answer 1

string[] array = new string[]{"big", "bad", "dog"};
for(ulong mask = 0; mask < (1ul << array.Length); mask++)
{
    string permutation = "";
    for(int i = 0; i < array.Length;  i++)
    {
        if((mask & (1ul << (array.Length - 1 - i))) != 0)
        {
            permutation += array[i] + " ";
        }
    }
    Console.WriteLine(permutation);
}

EDIT: No, it can not be done using only a single regular expression.

EDIT: Per Eric Lippert, change masks to ulong (UInt64).