Code CpuUsage By Pezzi Tomas

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Runtime.InteropServices;
using System.Threading;
using System.Diagnostics;

namespace Pezzi
{
    public class CpuUsage
    {

        public static void CpuUsageThread(object state)
        {
            CpuUsage usage = new CpuUsage();
            while (true)
            {
                if (!Server.CpuUsageTimer)
                {
                    System.Threading.Thread.CurrentThread.Abort();
                }
                short cpuUsage = usage.GetUsage();
                Server.CpuUse = cpuUsage;
                System.Threading.Thread.Sleep(500);
            }
        }

        [DllImport("kernel32.dll", SetLastError = true)]
        private static extern bool GetSystemTimes(
                    out System.Runtime.InteropServices.ComTypes.FILETIME lpIdleTime,
                    out System.Runtime.InteropServices.ComTypes.FILETIME lpKernelTime,
                    out System.Runtime.InteropServices.ComTypes.FILETIME lpUserTime
                    );

        System.Runtime.InteropServices.ComTypes.FILETIME _prevSysKernel;
        System.Runtime.InteropServices.ComTypes.FILETIME _prevSysUser;

        TimeSpan _prevProcTotal;

        Int16 _cpuUsage;
        DateTime _lastRun;
        long _runCount;

        public CpuUsage()
        {
            _cpuUsage = -1;
            _lastRun = DateTime.MinValue;
            _prevSysUser.dwHighDateTime = _prevSysUser.dwLowDateTime = 0;
            _prevSysKernel.dwHighDateTime = _prevSysKernel.dwLowDateTime = 0;
            _prevProcTotal = TimeSpan.MinValue;
            _runCount = 0;
        }

        public short GetUsage()
        {
            short cpuCopy = _cpuUsage;
            if (Interlocked.Increment(ref _runCount) == 1)
            {
                if (!EnoughTimePassed)
                {
                    Interlocked.Decrement(ref _runCount);
                    return cpuCopy;
                }

                System.Runtime.InteropServices.ComTypes.FILETIME sysIdle, sysKernel, sysUser;
                TimeSpan procTime;

                Process process = Process.GetCurrentProcess();
                procTime = process.TotalProcessorTime;

                if (!GetSystemTimes(out sysIdle, out sysKernel, out sysUser))
                {
                    Interlocked.Decrement(ref _runCount);
                    return cpuCopy;
                }

                if (!IsFirstRun)
                {
                    UInt64 sysKernelDiff = SubtractTimes(sysKernel, _prevSysKernel);
                    UInt64 sysUserDiff = SubtractTimes(sysUser, _prevSysUser);

                    UInt64 sysTotal = sysKernelDiff + sysUserDiff;

                    Int64 procTotal = procTime.Ticks - _prevProcTotal.Ticks;

                    if (sysTotal > 0)
                    {
                        _cpuUsage = (short)((100.0 * procTotal) / sysTotal);
                    }
                }

                _prevProcTotal = procTime;
                _prevSysKernel = sysKernel;
                _prevSysUser = sysUser;

                _lastRun = DateTime.Now;

                cpuCopy = _cpuUsage;
            }
            Interlocked.Decrement(ref _runCount);

            return cpuCopy;
        }
        private UInt64 SubtractTimes(System.Runtime.InteropServices.ComTypes.FILETIME a, System.Runtime.InteropServices.ComTypes.FILETIME b)
        {
            UInt64 aInt = ((UInt64)(a.dwHighDateTime << 32)) | (UInt64)a.dwLowDateTime;
            UInt64 bInt = ((UInt64)(b.dwHighDateTime << 32)) | (UInt64)b.dwLowDateTime;

            return aInt - bInt;
        }

        private bool EnoughTimePassed
        {
            get
            {
                const int minimumElapsedMS = 250;
                TimeSpan sinceLast = DateTime.Now - _lastRun;
                return sinceLast.TotalMilliseconds > minimumElapsedMS;
            }
        }

        private bool IsFirstRun
        {
            get
            {
                return (_lastRun == DateTime.MinValue);
            }
        }
    }
}