Question

I would like to retrieve the cpu and ram usage at that point for the foreground process (or a specific one).
Retrieving the window’s title is not a problem and that part works. But the cpu display stays at 0% even when the active window is running at 70% cpu or more.

(int)pCPU.NextValue(); // <<<< keeps returning 0…

Note: I want to do it with a performance counter. I don’t want to do it using the Process variable because that one might raise ‘insufficient privilege errors’.

    [DllImport("user32.dll")]
    static extern IntPtr GetForegroundWindow();

    [DllImport("user32.dll")]
    static extern int GetWindowText(IntPtr hWnd, StringBuilder text, int count);

    [DllImport("user32.dll")]
    public static extern IntPtr GetWindowThreadProcessId(IntPtr hWnd, out uint ProcessId);

    public void GetActiveCPUAndRam(out string windowTitle, out int CPUUsagePerc, out int RAMUsage)
    {
        IntPtr hwnd = GetForegroundWindow();
        uint pid;
        GetWindowThreadProcessId(hwnd, out pid);

        Process activeProc = Process.GetProcessById((int) pid);

        #region Window Title

        const int nChars = 256;
        StringBuilder Buff = new StringBuilder(nChars);
        if (GetWindowText(hwnd, Buff, nChars) > 0)
            windowTitle = Buff.ToString();
        else
        {
            windowTitle = "";
            CPUUsagePerc = 0;
            RAMUsage = 0;
            return;
        }

        #endregion

        #region RAM/CPU
        PerformanceCounter pCPU = new PerformanceCounter("Process", "% Processor Time", activeProc.ProcessName, true);
        pCPU.NextValue();
        CPUUsagePerc = (int)pCPU.NextValue(); // <<<<< problem here.

        RAMUsage = 0; // TODO:

        #endregion
    }

---

EDIT:
I tried the new solution:
But when I run a cpu stress test program that pushes the cpu usage to 100% (single core) . Then the solution below shows that the cpu usage of that process is like 300-400% of the total cpu… Obviously something is still wrong.

---

        private PerformanceCounter pCPU = null;
        private IntPtr PreviousProcHwnd = IntPtr.Zero;
        private CounterSample PreviousCPUCounterSample = CounterSample.Empty;

        public void GetActiveCPUAndRam(out string windowTitle, out int CPUUsagePerc, out int RAMUsage)
{
        ...
        #region RAM/CPU

        if (PreviousProcHwnd != hwnd)
        {
            PreviousProcHwnd = hwnd;
            pCPU = new PerformanceCounter("Process", "% Processor Time", activeProc.ProcessName,
                                                             true);
            PreviousCPUCounterSample = CounterSample.Empty;
        }

        CounterSample sample1 = pCPU.NextSample();
        CPUUsagePerc = (int)CounterSample.Calculate(PreviousCPUCounterSample, sample1);
        PreviousCPUCounterSample = sample1;
        RAMUsage = 0; // TODO:

        #endregion
}

Answer 1

Do not use the value directly, use the calculated sample,

CounterSample sample1 = pCPU.NextSample();
float value = CounterSample.Calculate(sample1);

if your counter is a ‘rate’ type sample, then you will need to get two samples,

CounterSample sample1 = counter.NextSample();
Thread.Sleep(1000); // wait some time
CounterSample sample2 = counter.NextSample();
float value = CounterSample.Calculate(sample1, sample2);