delayed_list.cs

var delayed_list = 
	from item in Enumerable.Range(0, 1000).DelayedList()
        where item%2 == 0
        select item*2;
// This is a 'delayed list'.
//Basically it is implicitly capable of producing a real List collection if we choose to force it.
//Before we do, we can just perform a few more LINQ queries...

var delayed_list2 =
	from item in delayed_list
	where item % 3 == 0
	select item;

//Right now, performing a second LINQ query basically disposes of the previous delayed list.
//We don't want to end up allocating lists for no reason after all.


//One way to force the evaluation of the list is an implicit conversion.

List<int> real_list = delayed_list2;

//Another way to force it is to iterate over it.
//However, because the delayed list has been evaluated iterating over it like this 
//Would just give us the List's IEnumerator. Meaning the list is cached internally.
foreach (var item in delayed_list2)
{
	Console.Write("{0}, ", item);
}
//We can do another LINQ query on it
var y = from item in x
        where item%4 == 0
        select item*9;

//Getting another delayed list.

//This has quite a few holes in it and is just for demonstration purposes.

//In general, it would work a lot better if instead of List we had an immutable data structure.