HashSet < string > companyTeams =new HashSet < string > (){ "Ferrari", "McLaren", "Toyota", "BMW","Renault", "Honda" };

HashSet < string > traditionalTeams =new HashSet < string > (){ "Ferrari", "McLaren" };

HashSet < string > privateTeams =new HashSet < string > (){ "Red Bull", "Toro Rosso", "Spyker","Super Aguri" };

if (privateTeams.Add("Williams"))
    Console.WriteLine("Williams added");
if (!companyTeams.Add("McLaren"))
    Console.WriteLine("McLaren was already in this set");

if (traditionalTeams.IsSubsetOf(companyTeams))
{
  Console.WriteLine("traditionalTeams is " +"subset of companyTeams");
}

if (companyTeams.IsSupersetOf(traditionalTeams))
{
  Console.WriteLine("companyTeams is a superset of " +"traditionalTeams");
}

traditionalTeams.Add("Williams");//前面代码中privateTeams已经加入该元素
if (privateTeams.Overlaps(traditionalTeams))
{
    Console.WriteLine("At least one team is " +"the same with the traditional " +"and privateteams");
}

HashSet < string > allTeams =new HashSet < string > (companyTeams);
allTeams.UnionWith(privateTeams);
allTeams.UnionWith(traditionalTeams);
Console.WriteLine();
Console.WriteLine("all teams");
foreach (var team in allTeams)
{
   Console.WriteLine(team);
}

allTeams.ExceptWith(privateTeams);
Console.WriteLine();
Console.WriteLine("no private team left");
foreach (var team in allTeams)
{
    Console.WriteLine(team);
}