Calculating process cpu usage from Process.TotalProcessorTime

Building upon 111WARLOCK111's answer, you can use the following minimal code to measure the current CPU load:

async Task<double> GetCpuLoadAsync(TimeSpan MeasurementWindow)
{
    Process CurrentProcess = Process.GetCurrentProcess();

    TimeSpan StartCpuTime = CurrentProcess.TotalProcessorTime;
    Stopwatch Timer = Stopwatch.StartNew();

    await Task.Delay(MeasurementWindow);

    TimeSpan EndCpuTime = CurrentProcess.TotalProcessorTime;
    Timer.Stop();

    return (EndCpuTime - StartCpuTime).TotalMilliseconds / (Environment.ProcessorCount * Timer.ElapsedMilliseconds);
}

Use the following code to call the function and replace the TimeSpan with the window to monitor:

double CpuLoad = await GetCpuLoadAsync(TimeSpan.FromSeconds(10));

class GetCPUUsage
{
    static TimeSpan start;
    public static double CPUUsageTotal
    {
        get;
        private set;
    }

    public static double CPUUsageLastMinute
    {
        get;
        private set;
    }

    static TimeSpan oldCPUTime = new TimeSpan(0);
    static DateTime lastMonitorTime = DateTime.UtcNow;
    public static DateTime StartTime = DateTime.UtcNow;
    // Call it once everything is ready
    static void OnStartup()
    {
        start = Process.GetCurrentProcess().TotalProcessorTime;
    }

    // Call this every 30 seconds
    static void CallCPU()
    {
        TimeSpan newCPUTime = Process.GetCurrentProcess().TotalProcessorTime - start;
        CPUUsageLastMinute = (newCPUTime - oldCPUTime).TotalSeconds / (Environment.ProcessorCount * DateTime.UtcNow.Subtract(lastMonitorTime).TotalSeconds);
        lastMonitorTime = DateTime.UtcNow;
        CPUUsageTotal = newCPUTime.TotalSeconds / (Environment.ProcessorCount * DateTime.UtcNow.Subtract(StartTime).TotalSeconds);
        oldCPUTime = newCPUTime;
    }
}

class GetCPUInfo
{
    public static string GetInfoMinute()
    {
        return String.Format("{0:0.0}", GetCPUUsage.CPUUsageLastMinute * 100);
    }

    public static string GetInfoTotal()
    {
        return String.Format("{0:0.0}", GetCPUUsage.CPUUsageTotal * 100);
    }
}