C# - Kernel Timer für Performancetests

using System;
using System.Runtime.InteropServices;

namespace OperationalManagement
{
	/// <summary>
	/// FxCop Rule CA1060.
	/// This type contains members with the DllImport attribute. 
	/// Members with the DllImport attribute should be contained 
	/// in classes named NativeMethods, SafeNativeMethods, 
	/// or UnsafeNativeMethods.
	/// </summary>
	internal sealed class NativeMethods
	{
		/// <summary>
		/// private Ctor for static Class.
		/// </summary>
		private NativeMethods()
		{
		}

		/// <summary>
		/// DllImport von KERNEL32.
		/// </summary>
		/// <param name="nPfCt">Performancecounter.</param>
		/// <returns>true oder false.</returns>
		[DllImport("KERNEL32")]
		[return : MarshalAs(UnmanagedType.Bool)]
		internal static extern bool QueryPerformanceCounter(ref Int64 nPfCt);

		/// <summary>
		/// DllImport von KERNEL32.
		/// </summary>
		/// <param name="nPfFreq">Ferequenz.</param>
		/// <returns>true oder false.</returns>
		[DllImport("KERNEL32")]
		[return : MarshalAs(UnmanagedType.Bool)]
		internal static extern bool QueryPerformanceFrequency(ref Int64 nPfFreq);
	}

	/// <summary>
	/// For Performancetestings
	/// </summary>
	public sealed class KernelTimer
	{
		private Int64 _i64Frequency;
		private Int64 _i64Start;

		/// <summary>
		/// startet den Timer
		/// </summary>
		public void Start()
		{
			Reset();
			NativeMethods.QueryPerformanceCounter(ref _i64Start);
		}

		/// <summary>
		/// Zurücksetzen
		/// </summary>
		public void Reset()
		{
			NativeMethods.QueryPerformanceFrequency(ref _i64Frequency);
			_i64Start = 0;
		}

		/// <summary>
		/// stopt den Timer und liefert das Resultat
		/// </summary>
		/// <returns>double-Wert.</returns>
		public double End()
		{
			Int64 i64End = 0;
			NativeMethods.QueryPerformanceCounter(ref i64End);
			return ((i64End - _i64Start)/(double) _i64Frequency);
		}
	}
}