Why is function isprefix faster than Startswith in C#?

Question

Does anyone know why C# (.NET)\'s StartsWith function is considerably slower than IsPrefix?

Answer 1

Good question; for a test, I get:

9156ms; chk: 50000000
6887ms; chk: 50000000

Test rig:

using System;
using System.Diagnostics;
using System.Globalization;    

class Program
{
    static void Main()
    {
        string s1 = "abcdefghijklmnopqrstuvwxyz", s2 = "abcdefg";

        const int LOOP = 50000000;
        int chk = 0;
        Stopwatch watch = Stopwatch.StartNew();
        for (int i = 0; i < LOOP; i++)
        {
            if (s1.StartsWith(s2)) chk++;
        }
        watch.Stop();
        Console.WriteLine(watch.ElapsedMilliseconds + "ms; chk: " + chk);

        chk = 0;
        watch = Stopwatch.StartNew();

        CompareInfo ci = CultureInfo.CurrentCulture.CompareInfo;
        for (int i = 0; i < LOOP; i++)
        {
            if (ci.IsPrefix(s1, s2)) chk++;
        }
        watch.Stop();
        Console.WriteLine(watch.ElapsedMilliseconds + "ms; chk: " + chk);
    }
}