包含不重复元素的集合称为“集（set）”。.NET Framework包含两个集HashSet<T>和SortedSet<T>，它们都实现ISet<T>接口。HashSet<T>集包含不重复元素的无序列表，SortedSet<T>集包含不重复元素的有序列表。
ISet<T>接口提供的方法可以创建合集，交集，或者给出一个是另一个集的超集或子集的信息。
var companyTeams = new HashSet<string>() { "Ferrari", "McLaren", "Mercedes" };
var traditionalTeams = new HashSet<string>() { "Ferrari", "McLaren" };
var privateTeams = new HashSet<string>() { "Red Bull", "Lotus", "Toro Rosso", "Force India", "Sauber" };
if (privateTeams.Add("Williams"))
Console.WriteLine("Williams added");
if (!companyTeams.Add("McLaren"))
Console.WriteLine("McLaren was already in this set");
IsSubsetOf验证traditionalTeams中的每个元素是否都包含在companyTeams中
if (traditionalTeams.IsSubsetOf(companyTeams))
{
Console.WriteLine("traditionalTeams is subset of companyTeams");
}
IsSupersetOf验证traditionalTeams中是否有companyTeams中没有的元素
if (companyTeams.IsSupersetOf(traditionalTeams))
{
Console.WriteLine("companyTeams is a superset of traditionalTeams");
}
Overlaps验证是否有交集
traditionalTeams.Add("Williams");
if (privateTeams.Overlaps(traditionalTeams))
{
Console.WriteLine("At least one team is the same with the traditional " +
"and private teams");
}
调用UnionWith方法把新的 SortedSet<string>变量填充为companyTeams，privateTeams，traditionalTeams的合集
var allTeams = new SortedSet<string>(companyTeams);
allTeams.UnionWith(privateTeams);
allTeams.UnionWith(traditionalTeams);
Console.WriteLine();
Console.WriteLine("all teams");
foreach (var team in allTeams)
{
Console.WriteLine(team);
}
输出（有序的）：
Ferrari
Force India
Lotus
McLaren
Mercedes
Red Bull
Sauber
Toro Rosso
Williams
每个元素只列出一次，因为集只包含唯一值。
ExceptWith方法从ExceptWith中删除所有私有元素
allTeams.ExceptWith(privateTeams);
Console.WriteLine();
Console.WriteLine("no private team left");
foreach (var team in allTeams)
{
Console.WriteLine(team);
}
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