Pick n items from a set of items

PickItems.cs

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

public class Class1
{
	public static IEnumerable<Class1> SomeMethodThatReturnsAllCardsAvailable()
	{
		return null;
	}

	public static int RandomNumberGenerator(int minInclusive, int maxExclusive)
	{
		new Random().Next();//dont actually use this
		return 0;
	}

	public static IEnumerable<Class1> PickCards(int amount)
	{
		List<Class1> pickedCards = new List<Class1>();
		var remainingCards = SomeMethodThatReturnsAllCardsAvailable();

		var count = remainingCards.Count();
		while (amount > 0 && count > 0)
		{
			//Invariants:
			//we still want to draw cards (amount > 0)
			//there are cards that we can draw (_.Count() > 0)
			var index = RandomNumberGenerator(0, remainingCards.Count());
			var card = remainingCards.ElementAt(index);
			pickedCards.Add(card);

			remainingCards = remainingCards.Except(card);
			amount--;
			//Invariant:
			//count will describe the cards available
			count = remainingCards.Count();
		}

		return pickedCards;
	}
}