CombinatoricsSubsetsT Method (ISetT, Boolean)

public static IEnumerable<SortedSet<T>> Subsets<T>(
	this ISet<T> set,
	bool inPlace = false
)

<ExtensionAttribute>
Public Shared Function Subsets(Of T) ( 
	set As ISet(Of T),
	Optional inPlace As Boolean = false
) As IEnumerable(Of SortedSet(Of T))

// Let's say we would like to compute all the
// possible subsets of the set { 1, 2, 3, 4 }:
// 
ISet<int> set = new HashSet<int> { 1, 2, 3, 4 };

// The number of possible subsets might be too large
// to fit on memory. For this reason, we can compute
// values on-the-fly using foreach:

foreach (SortedSet<int> subset in Combinatorics.Subsets(set))
{
    // ...
}

// Or we could try to compute them all and store in an array:
SortedSet<int>[] subsets = Combinatorics.Subsets(set).ToArray();

// In either case, the result will be:

int[][] expected =
{
   new [] { 1 },
   new [] { 2 },
   new [] { 3 },
   new [] { 4 },
   new [] { 1, 2 },
   new [] { 1, 3 },
   new [] { 2, 3 },
   new [] { 1, 4 },
   new [] { 2, 4 },
   new [] { 3, 4 },
   new [] { 1, 2, 3 },
   new [] { 1, 2, 4 },
   new [] { 1, 3, 4 },
   new [] { 2, 3, 4 },
   new [] { 1, 2, 3, 4 }
};

// Note: although the empty set is technically a subset
// of all sets, it won't be included in the enumeration