如何使用带有计时器刻度的BackgroundWorker？

Question

Decided to not use any timers. What i did is simpler.

Added a backgroundworker. Added a Shown event the Shown event fire after all the constructor have been loaded. In the Shown event im starting the backgroundworker async.

In the backgroundworker DoWork im doing:

private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
        {
            while(true)
            {
                cpuView();
                gpuView();
                Thread.Sleep(1000);
            }
        }

Answer 1

In this case it's better to use two System.Threading.Timer and execute your cpu-intensive operations in these two threads. Please note that you must access controls with BeginInvoke . You can encapsulate those accesses into properties setter or even better pull them out to a view model class.

public class MyForm : Form
{
    private System.Threading.Timer gpuUpdateTimer;
    private System.Threading.Timer cpuUpdateTimer;

    protected override void OnLoad(EventArgs e)
    {
        base.OnLoad(e);

        if (!DesignMode)
        {
            gpuUpdateTimer = new System.Threading.Timer(UpdateGpuView, null, 0, 1000);
            cpuUpdateTimer = new System.Threading.Timer(UpdateCpuView, null, 0, 100);
        }
    }

    private string GpuText
    {
        set
        {
            if (InvokeRequired)
            {
                BeginInvoke(new Action(() => gpuLabel.Text = value), null);
            }
        }
    }

    private string TemperatureLabel
    {
        set
        {
            if (InvokeRequired)
            {
                BeginInvoke(new Action(() => temperatureLabel.Text = value), null);
            }
        }
    }

    private void UpdateCpuView(object state)
    {
        // do your stuff here
        // 
        // do not access control directly, use BeginInvoke!
        TemperatureLabel = sensor.Value.ToString() + "c" // whatever
    }

    private void UpdateGpuView(object state)
    {
        // do your stuff here
        // 
        // do not access control directly, use BeginInvoke!
        GpuText = sensor.Value.ToString() + "c";  // whatever
    }

    protected override void Dispose(bool disposing)
    {
        if (disposing)
        {
            if (cpuTimer != null)
            {
                cpuTimer.Dispose();
            }
            if (gpuTimer != null)
            {
                gpuTimer.Dispose();
            }
        }

        base.Dispose(disposing);
    }

Answer 2

You can't just throw this code into a background worker and expect it to work. Anything that updates UI elements (labels, textboxes, ...) needs to be invoked on the main thread. You need to break out your logic to get the data and the logic to update the UI.

I would say your best bet is to do this:

In the timer Tick() method:

// Disable the timer.
// Start the background worker

In the background worker DoWork() method:

// Call your functions, taking out any code that 
// updates UI elements and storing this information 
// somewhere you can access it once the thread is done.

In the background worker Completed() method:

// Update the UI elements based on your results from the worker thread
// Re-enable the timer.

Answer 3

First make sure to get your head around multithreathing and it's problems (especially UI stuff).

Then you can use somethink like

public class Program
{
    public static void Main(string[] args)
    {
        Timer myTimer = new Timer(TimerTick, // the callback function
            new object(), // some parameter to pass
            0, // the time to wait before the timer starts it's first tick
            1000); // the tick intervall
    }

    private static void TimerTick(object state)
    {
        // less then .NET 4.0
        Thread newThread = new Thread(CallTheBackgroundFunctions);
        newThread.Start();

        // .NET 4.0 or higher
        Task.Factory.StartNew(CallTheBackgroundFunctions);
    }

    private static void CallTheBackgroundFunctions()
    {
        cpuView();
        gpuView();
    }
}

Please keep in mind (just like John Koerner told you) your cpuView() and gpuView() will not work as is.

Answer 4

Yes you can:

In your Timer tick event:

private void timer_Tick(object sender, EventArgs e)
{

  timer.Enabled = false;

  backgroundworker.RunWorkerAsync();

  timer.Enabled = true;
}

In your Backgroundworker dowork event:

private void backgroundworker_DoWork(object sender, System.ComponentModel.DoWorkEventArgs e)
{
   try
   {
       //Write what you want to do
   }
   catch (Exception ex)
   {
       MessageBox.Show("Error:\n\n" + ex.Message, "System", MessageBoxButtons.OK, MessageBoxIcon.Error);
   }
}

Answer 5

I think BackgroundWorker is too complex thing for the case; with Timer it is difficult to implement guaranteed stopping.

I would like to recommend you using worker Thread with the loop which waits cancellation ManualResetEvent for the interval you need:

• If the cancellation event is set then the worker exits the loop.
• If there is a timeout (time interval you need exceeds) then perform system monitoring.

Here is the draft version of the code. Please note I have not tested it , but it could show you the idea.

public class HardwareMonitor
{
    private readonly object _locker = new object();
    private readonly TimeSpan _monitoringInterval;
    private readonly Thread _thread;
    private readonly ManualResetEvent _stoppingEvent = new ManualResetEvent(false);
    private readonly ManualResetEvent _stoppedEvent = new ManualResetEvent(false);

    public HardwareMonitor(TimeSpan monitoringInterval)
    {
        _monitoringInterval = monitoringInterval;
        _thread = new Thread(ThreadFunc)
            {
                IsBackground = true
            };
    }

    public void Start()
    {
        lock (_locker)
        {
            if (!_stoppedEvent.WaitOne(0))
                throw new InvalidOperationException("Already running");

            _stoppingEvent.Reset();
            _stoppedEvent.Reset();
            _thread.Start();
        }
    }

    public void Stop()
    {
        lock (_locker)
        {
            _stoppingEvent.Set();
        }
        _stoppedEvent.WaitOne();
    }

    private void ThreadFunc()
    {
        try
        {
            while (true)
            {
                // Wait for time interval or cancellation event.
                if (_stoppingEvent.WaitOne(_monitoringInterval))
                    break;

                // Monitoring...
                // NOTE: update UI elements using Invoke()/BeginInvoke() if required.
            }
        }
        finally
        {
            _stoppedEvent.Set();
        }
    }
}

Answer 6

In my case I was using a BackgroundWorker ,a System.Timers.Timer and a ProgressBar in WinForm Application. What I came across is on second tick that I will repeat the BackgroundWorker's Do-Work I get a Cross-Thread Exception while trying to update ProgressBar in ProgressChanged of BackgroundWorker .Then I found a solution on SO @Rudedog2 https://stackoverflow.com/a/4072298/1218551 which says that When you initialize the Timers.Timer object for use with a Windows Form, you must set the SynchronizingObject property of the timer instance to be the form.

systemTimersTimerInstance.SynchronizingObject = this; // this = form instance.

http://msdn.microsoft.com/en-us/magazine/cc164015.aspx