How to optimize and pre-compile this LINQ expression?

Question

Given the following input against 60% toleration

"STACKOVERflow is a quesTions and ANSwers weBSITE"

I expect the following output

// Extra spaces just to show %s
// 69%          50%  100%  22%!      33% 42%     14%
"Stackoverflow  Is   A     QuesTions And ANSwers Website"

Questions and Answers have uppercase characters but they represent less than 60% of the string, so it should be kept. And then I want to convert the first character of each string to uppercase.

I'm currently doing with this method

public static class StringExtender
{
    public static string ToTitleCase(this string str, double preserve)
    {
        return String.Join(" ",
            str.Split(' ')
            .Select(x => (x.Count(y => y.ToString() == y.ToString().ToUpper()) / (double)x.Length * 100) > preserve ? x.ToLower() : x)
            .Select(x =>
                String.Join(String.Empty,
                    x.Select((y, z) => z == 0 ? y.ToString().ToUpper() : y.ToString()).ToArray()
                )
            ).ToArray()
        );
    }
}

The first time it runs I get 15000 ticks (Stopwatch.EllapsedTicks) and the next ones runs at 300. It seems the first time it does some kind of compilation...

• Is there some way to compile it not in runtime, so the first time it runs it uses full speed just like the next?
• Is there a way to optimize this code even more?

---

Full code (to include measurement methods)

using System;
using System.Diagnostics;
using System.Linq;

public static class StopwatchExtender
{
    public static void Timer(this Stopwatch sw, Action x, int iterations, string name)
    {
        sw.Start();
        for (int i = 0; i < iterations; ++i)
        {
            x();
        }
        sw.Stop();

        Console.WriteLine("Name: {0}\nTicks: {1}\n", name, sw.ElapsedTicks);

        sw.Reset();
    }
}

public static class StringExtender
{
    public static string OP(this string str, double preserve)
    {
        return String.Join(" ",
            str.Split(' ')
            .Select(x => (x.Count(y => y.ToString() == y.ToString().ToUpper()) / (double)x.Length * 100) > preserve ? x.ToLower() : x)
            .Select(x =>
                String.Join(String.Empty,
                    x.Select((y, z) => z == 0 ? y.ToString().ToUpper() : y.ToString()).ToArray()
                )
            ).ToArray()
        );
    }

    public static string A01(this string str, double preserve)
    {
        return string.Join(" ",
            str.Split(' ')
                .Select(s => char.ToUpper(s[0]) + ((s.Count(c => char.IsUpper(c)) / (double)s.Length * 100) > preserve ? s.Substring(1).ToLower() : s.Substring(1)))
                .ToArray()
            );
    }
}

public class Program
{
    static void Main()
    {
        var sw = new Stopwatch();

        var str = "STACKOVERflow is a quesTions and ANSwers weBSITE";

        sw.Timer(() =>
        {
            str.OP(60);
            str.A01(60);
        }, 1, "Starup takes more time");

        sw.Timer(() =>
        {
            str.OP(60);
        }, 1000000, "OP solution");

        sw.Timer(() =>
        {
            str.A01(60);
        }, 1000000, "LukeH's answer");

        Console.ReadLine();
    }
}

Results

Answer 1

This isn't really answering your question but a TitleCase() method has been in the .NET Framework for some time... check out the TextInfo class: http://msdn.microsoft.com/en-us/library/system.globalization.textinfo.totitlecase.aspx

Answer 2

public static string ToTitleCase(this string str, double preserve)
{
    return string.Join(" ",
        str.Split(' ')
           .Select(s => s.Length == 0 ? s : char.ToUpper(s[0]) + ((s.Count(c => char.IsUpper(c)) / (double)s.Length * 100) > preserve ? s.Substring(1).ToLower() : s.Substring(1)))
           .ToArray());
}

(And don't forget to remove that final ToArray call if you're using .NET 4.)