HashSet<T>.Overlaps Method

static void Main()
{
    HashSet<int> lowNumbers = new HashSet<int>();
    HashSet<int> allNumbers = new HashSet<int>();

    for (int i = 1; i < 5; i++)
    {
        lowNumbers.Add(i);
    }

    for (int i = 0; i < 10; i++)
    {
        allNumbers.Add(i);
    }

    Console.Write("lowNumbers contains {0} elements: ", lowNumbers.Count);
    DisplaySet(lowNumbers);

    Console.Write("allNumbers contains {0} elements: ", allNumbers.Count);
    DisplaySet(allNumbers);

    Console.WriteLine("lowNumbers overlaps allNumbers: {0}",
        lowNumbers.Overlaps(allNumbers));

    Console.WriteLine("allNumbers and lowNumbers are equal sets: {0}",
        allNumbers.SetEquals(lowNumbers));

    // Show the results of sub/superset testing
    Console.WriteLine("lowNumbers is a subset of allNumbers: {0}",
        lowNumbers.IsSubsetOf(allNumbers));
    Console.WriteLine("allNumbers is a superset of lowNumbers: {0}",
        allNumbers.IsSupersetOf(lowNumbers));
    Console.WriteLine("lowNumbers is a proper subset of allNumbers: {0}",
        lowNumbers.IsProperSubsetOf(allNumbers));
    Console.WriteLine("allNumbers is a proper superset of lowNumbers: {0}",
        allNumbers.IsProperSupersetOf(lowNumbers));

    // Modify allNumbers to remove numbers that are not in lowNumbers.
    allNumbers.IntersectWith(lowNumbers);
    Console.Write("allNumbers contains {0} elements: ", allNumbers.Count);
    DisplaySet(allNumbers);

    Console.WriteLine("allNumbers and lowNumbers are equal sets: {0}",
        allNumbers.SetEquals(lowNumbers));

    // Show the results of sub/superset testing with the modified set.
    Console.WriteLine("lowNumbers is a subset of allNumbers: {0}",
        lowNumbers.IsSubsetOf(allNumbers));
    Console.WriteLine("allNumbers is a superset of lowNumbers: {0}",
        allNumbers.IsSupersetOf(lowNumbers));
    Console.WriteLine("lowNumbers is a proper subset of allNumbers: {0}",
        lowNumbers.IsProperSubsetOf(allNumbers));
    Console.WriteLine("allNumbers is a proper superset of lowNumbers: {0}",
        allNumbers.IsProperSupersetOf(lowNumbers));
}
/* This code example produces output similar to the following:
 * lowNumbers contains 4 elements: { 1 2 3 4 }
 * allNumbers contains 10 elements: { 0 1 2 3 4 5 6 7 8 9 }
 * lowNumbers overlaps allNumbers: True
 * allNumbers and lowNumbers are equal sets: False
 * lowNumbers is a subset of allNumbers: True
 * allNumbers is a superset of lowNumbers: True
 * lowNumbers is a proper subset of allNumbers: True
 * allNumbers is a proper superset of lowNumbers: True
 * allNumbers contains 4 elements: { 1 2 3 4 }
 * allNumbers and lowNumbers are equal sets: True
 * lowNumbers is a subset of allNumbers: True
 * allNumbers is a superset of lowNumbers: True
 * lowNumbers is a proper subset of allNumbers: False
 * allNumbers is a proper superset of lowNumbers: False
 */