Finding Fibonacci sequence in C#. [Project Euler Exercise]

Question

I\'m having some trouble with this problem in Project Euler.

Here\'s what the question asks:

Each new term in the Fibonacci sequence is generated by adding t

Answer 1

The trickier way:

//1: Allow declaring of recursive functions
private delegate Func FuncRec(FuncRec f);
static Func RecFunction(Func, Func> f)
{
    FuncRec funcRec = r => t => f(r(r))(t);
    return funcRec(funcRec);
}

//Define the factorial function
public static readonly Func Fibonacci 
        = RecFunction(fib => n =>
            (n == 1 || n == 0)
            ? n
            : fib(n - 1) + fib(n - 2)); 

//Make a "continous" version
static IEnumerable ContinousFibonacci()
    {
        ulong count = 0;
        while(true)
        {
            ulong n = Fibonacci(count);
            count++;
            yield return n;
        }
    }

//Linq result
static void Main(string[] args)
    {


        ulong result = ContinousFibonacci()
            .TakeWhile(r => r < 4000000)
            .Where(IsEven)
            .Aggregate(0,(current, s) => (s + current));

        Console.WriteLine(result);
        Console.ReadLine();

    }

///The Functional-Style method of allowing one to create recursive functions such as above was made by Bart De Smet. See http://bartdesmet.net/blogs/bart/archive/2009/11/08/jumping-the-trampoline-in-c-stack-friendly-recursion.aspx