using System;

using System.Collections.Generic;

using System.Linq;

​

public class Program

{

    public static void Main()

    {

        Console.WriteLine("GetObjects(Type):");

        Console.WriteLine(GetObjects(typeof(Foo)));

        Console.WriteLine();

        Console.WriteLine("GetObjects<Type>():");

        Console.WriteLine(GetObjects<Bar>());

        Console.WriteLine();

        var x = new Quux { a = 1, b = 2 };

        var y = new Quux { a = 1, b = 2 };

        var z = new Quux { a = 3, b = 4 };

        var qs = new Quux[] { x };

        Console.WriteLine("array contains:");

        Console.WriteLine(qs.Contains(y));

        Console.WriteLine(qs.Contains(z));

        Console.WriteLine();

        Console.WriteLine("array contains (with comparer):");

        Console.WriteLine(qs.Contains(y, new QuuxComparer()));

        Console.WriteLine(qs.Contains(z, new QuuxComparer()));

        Console.WriteLine();

        var qsh = qs.ToHashSet();

        Console.WriteLine("hashset contains:");

        Console.WriteLine(qsh.Contains(y));

        Console.WriteLine(qsh.Contains(z));

        Console.WriteLine();

        Console.WriteLine("hashset contains (with comparer):");

        Console.WriteLine(qsh.Contains(y, new QuuxComparer()));

        Console.WriteLine(qsh.Contains(z, new QuuxComparer()));

        Console.WriteLine();

    }

    struct Quux

    {

        public int a;

        public int b;

    }

    class QuuxComparer : IEqualityComparer<Quux>

    {

        public bool Equals(Quux q1, Quux q2)

        {

            return q1.a == q2.a

                && q1.b == q2.b;

        }

        public int GetHashCode(Quux q)

        {

            unchecked

            {

                return q.a.GetHashCode() * 17 + q.b.GetHashCode();

            }

        }

    }

    public class Foo {}

    public class Bar {}

    public static object[] GetObjects(Type t)

    {

        if (t == typeof(Foo))

            return new Foo[1];

        if (t == typeof(Bar))

            return new Bar[2];

        return null;

    }

    public static IEnumerable<T> GetObjects<T>()

    {

        return GetObjects(typeof(T)).Cast<T>();

    }

}