HashSet<T>のメソッドの使い方

gistfile1.cs

using System;
using System.Collections.Generic;
using System.Linq;

namespace ConsoleApp {
	class Program {
		static void Main( string[] args ) {
			var items = new HashSet<int> { 0, 1, 2, 3, 4, };

			// otherが同じ要素を含んでいるかどうか
			Console.WriteLine( "SetEquals(other)" );
			Console.WriteLine( items.SetEquals( new[] { 0, 1, 2, 3, 4, } ) );		// True
			Console.WriteLine( items.SetEquals( new[] { 0, 1, 2, 3, } ) );			// False
			Console.WriteLine( items.SetEquals( new[] { 0, 1, 2, 3, 4, 5, } ) );	// False

			// otherの部分(下位)集合かどうか
			Console.WriteLine( "IsSubsetOf(other)" );
			Console.WriteLine( items.IsSubsetOf( new[] { 0, 1, 2, 3, 4, } ) );		// True
			Console.WriteLine( items.IsSubsetOf( new[] { 0, 1, 2, 3, } ) );			// False
			Console.WriteLine( items.IsSubsetOf( new[] { 0, 1, 2, 3, 4, 5, } ) );	// True

			// otherの真部分(下位)集合かどうか
			Console.WriteLine( "IsProperSubsetOf(other)" );
			Console.WriteLine( items.IsProperSubsetOf( new[] { 0, 1, 2, 3, 4, } ) );	// False
			Console.WriteLine( items.IsProperSubsetOf( new[] { 0, 1, 2, 3, } ) );		// False
			Console.WriteLine( items.IsProperSubsetOf( new[] { 0, 1, 2, 3, 4, 5, } ) );	// True

			// otherの上位集合かどうか
			Console.WriteLine( "IsSupersetOf(other)" );
			Console.WriteLine( items.IsSupersetOf( new[] { 0, 1, 2, 3, 4, } ) );	// True
			Console.WriteLine( items.IsSupersetOf( new[] { 0, 1, 2, 3, } ) );		// True
			Console.WriteLine( items.IsSupersetOf( new[] { 0, 1, 2, 3, 4, 5, } ) );	// False

			// otherの真?上位集合かどうか
			Console.WriteLine( "IsProperSupersetOf(other)" );
			Console.WriteLine( items.IsProperSupersetOf( new[] { 0, 1, 2, 3, 4, } ) );		// False
			Console.WriteLine( items.IsProperSupersetOf( new[] { 0, 1, 2, 3, } ) );			// True
			Console.WriteLine( items.IsProperSupersetOf( new[] { 0, 1, 2, 3, 4, 5, } ) );	// False

			// 実行結果
			/*
			SetEquals(other)
			True
			False
			False
			IsSubsetOf(other)
			True
			False
			True
			IsProperSubsetOf(other)
			False
			False
			True
			IsSupersetOf(other)
			True
			True
			False
			IsProperSupersetOf(other)
			False
			True
			False
			*/
		}
	}
}