Need a high resolution timer

I like to profile my code regularly to see if any changes I make during development affect performance. In .Net 1.1 there is a distinct lack of a high resolution timer object. Here's one you can use:

using System;
using System.Diagnostics;
using System.Runtime.InteropServices;
using System.ComponentModel;
using System.Threading;

namespace myNamespace
{
    [DebuggerStepThrough()]
    public class HiPerfTimer
    {
        [DllImport("Kernel32.dll")]
        private static extern bool QueryPerformanceCounter(
            ref long lpPerformanceCount);

        [DllImport("Kernel32.dll")]
        private static extern bool QueryPerformanceFrequency(
            ref long lpFrequency);

        private long startTime, stopTime;
        private long freq;

        // Constructor
        public HiPerfTimer()
        {
            startTime = 0;
            stopTime  = 0;

            if (QueryPerformanceFrequency(ref freq) == false)
            {
                // high-performance counter not supported
                throw new Win32Exception();
            }
        }

        // Start the timer
        public void Start()
        {
            // lets the waiting threads do their work
            Thread.Sleep(0);

            QueryPerformanceCounter(ref startTime);
        }

        // Stop the timer
        public void Stop()
        {
            QueryPerformanceCounter(ref stopTime);
        }

        // Returns the duration of the timer
        public double Duration
        {
            get
            {
                return (double)(stopTime - startTime) / (double) freq;
            }
        }
    }
}

Call like this:

HiPerfTimer myTimer = new HiPerfTimer();

myTimer.Start();

//Do some stuff that needs timing here...

myTimer.Stop();

MessageBox.Show(myTimer.Duration.ToString())