HashSet<T>类主要是设计用来做高性能集运算的，例如对两个集合求交集、并集、差集等

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 = 1; i < 5; i++)
{
allNumbers.Add(i);
}

 

//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);

//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));

Console.ReadLine();
}