I have an observer with a background worker. Lets say the observer has the following structure:
internal class Observer
{
private readonly BackgroundWorker bw1;
internal Object target;
public Observer()
{
bw1 = new BackgroundWorker();
bw1.DoWork += bw1_DoWork;
bw1.RunWorkerCompleted += bw1_RunWorkerCompleted;
bw1.WorkerSupportsCancellation = true;
}
private void bw1_DoWork(object sender, DoWorkEventArgs e)
{
e.Result = new object(); // Query to database
}
private void bw1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
target = e.Result as object;
if (ChangedScannedValue != null)
{
ChangedScannedValue(_scannedValue);
}
}
private String _scannedValue = string.Empty;
internal delegate void OnChangedScannedValue(String scannedValue);
internal event OnChangedScannedValue ChangedScannedValue;
internal String ScannedValue
{
get { return _scannedValue; }
set
{
_scannedValue = value;
bw1.RunWorkerAsync(_scannedValue);
//ProcessScannedValue();
}
}
}
I have another class listening to the event.
public partial class myControl : UserControl
{
Observer _observer = new Observer();
public myControl()
{
InitializeComponent();
}
internal void LoadData(Observer observer)
{
_observer = observer;
_observer.ChangedScannedValue += _observer_ChangedScannedValue;
}
void _observer_ChangedScannedValue(string ScannedValue)
{
if (_observer.target != null)
{
// Do Stuff
}
else
{
MessageBox.Show("NO TARGET FOUND.");
}
}
}
The thing is. initially, after the background worker finishes, I get the message box "NO TARGET FOUND.", however immediatley after, it would //Do Stuff Debugging shows that the RunWorkerCompleted event fires twice. This only happens on the first change to scanned value, all changes afterwards work as desired.
Questions:
1) Why does RunWorkerCompleted fire twice?
2) Why is the target not updated on the first fire of RunWorkerCompleted
You could try again with target being set in bw1_DoWork already, i.e.:
private void bw1_DoWork(object sender, DoWorkEventArgs e) {
target = new object(); // Query to database
}
private void bw1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e) {
if (ChangedScannedValue != null) {
ChangedScannedValue(_scannedValue);
}
}
Eventually you may want to replace the BackgroundWorker by a simpler solution with ThreadPool. I'd suggest this:
internal String ScannedValue {
get { return _scannedValue; }
set {
_scannedValue = value;
ThreadPool.QueueUserWorkItem( (WaitCallback) delegate {
target = new object(); // query database
if (ChangedScannedValue != null) ChangedScannedValue(_scannedValue);
} );
}
}
Related
In the overrided void onIncomingCall I open a new Background thread which shows a new (Popup) Form.
I try to pickup or decline the Call in this Form but then I get an System.AccessViolationException.
it seems that the current call object is locked and cannot be accessed from another Form.
If I use the currentcall.answer(prm) in the onIncomingCall void then the call is established successfully (without another Form and thread).
public class myaccount : Account
{
public override void onIncomingCall(OnIncomingCallParam prm)
{
Call call = new Call(this, prm.callId);
CallOpParam param = new CallOpParam();
param.statusCode = pjsip_status_code.PJSIP_SC_RINGING;
param.statusCode = pjsip_status_code.PJSIP_SC_OK;
pjsipfunctions.currentparam = param;
pjsipfunctions.currentcall = call;
var thread = new Thread(() =>
{
ShowPopup(call,prm.callId.ToString());
});
thread.SetApartmentState(ApartmentState.STA);
thread.Start();
// Thread myCallingThread = new Thread(new ThreadStart(ShowPopup));
//myCallingThread.SetApartmentState(ApartmentState.STA);
//myCallingThread.IsBackground = true;
//myCallingThread.Start();
}
public void ShowPopup(Call myCall,string call_id)
{
IncommingCallPopup win = new IncommingCallPopup(ref myCall, call_id );
win.Show();
System.Windows.Threading.Dispatcher.Run();
}
}
#####################################
public IncommingCallPopup(ref Call info, string callid)
{
currentCall = info;
Callid = callid;
CurrentCall = currentCall;
Prm.statusCode = pjsip_status_code.PJSIP_SC_RINGING;
InitializeComponent();
labelCallId.Content = callid;
}
private void rejectcall(object sender, RoutedEventArgs e)
{
Prm.statusCode = pjsip_status_code.PJSIP_SC_DECLINE;
CurrentCall.hangup(Prm);
}
private void transfercall(object sender, RoutedEventArgs e)
{
}
private void takecall(object sender, RoutedEventArgs e)
{
Prm.statusCode = pjsip_status_code.PJSIP_SC_OK;
try
{
CurrentCall.answer(Prm);
}
catch(Exception ex)
{
}
}
After crazy searching and trying some things i've figured it out.
Every Thread must registered in the Endpoint that you can hangup, pickup or transfer your call in another Class(Window).
All you need is to write this Method in a Public class and call this void everytime you call your void from another window ->
public void callpopup(String number) {
checkThread();
//answer, decline or something else
}
[MethodImpl(MethodImplOptions.Synchronized)]
public static void checkThread()
{
try
{
if (ep != null && !ep.libIsThreadRegistered())
ep.libRegisterThread(Thread.CurrentThread.Name);
}
catch (Exception e)
{
}
}
i want to just stop my backgroundworker when i press a button :
Code looking like :
Button :
private void button6_Click(object sender, EventArgs e)
{
backgroundWorker1.WorkerReportsProgress = true;
backgroundWorker1.WorkerSupportsCancellation = true;
if (isOn == true)
{
isOn = false;
if (!backgroundWorker1.IsBusy)
{
backgroundWorker1.RunWorkerAsync();
this.button6.ForeColor = System.Drawing.Color.Lime;
}
}
else
{
isOn = true;
this.button6.ForeColor = System.Drawing.Color.Red;
backgroundWorker1.CancelAsync();
//////backgroundWorker1.Dispose();
}
And my Backgroundworker_DoWork look like :
private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
if (backgroundWorker1.CancellationPending && backgroundWorker1.IsBusy)
{
e.Cancel = true;
return;
}
while (true)
{
if (backgroundWorker1.CancellationPending && backgroundWorker1.IsBusy)
{
e.Cancel = true;
break;
}
backgroundWorker1.Dispose();
click_na_default(hwnd1);
click_F8(hwnd1);
click_na_YELLS(hwnd1);
click_ENTER(hwnd1);
Thread.Sleep(100);
click_na_trade(hwnd1);
Thread.Sleep(100);
click_F8(hwnd1);
click_ENTER(hwnd1);
Thread.Sleep(100);
click_na_default(hwnd1);
Thread.Sleep(4000);
}
if (((BackgroundWorker)sender).CancellationPending)
{
e.Cancel = true;
//set this code at the end of file processing
return;
}
}
And the problem is : I can't .CancelAsync(); just immediately after button press again . My code just DoWork untill just Thread.Sleep(4000); is over.
When i press my button to stop work this gonna stop just after end while loop.
I know i can add
if (backgroundWorker1.CancellationPending && backgroundWorker1.IsBusy)
{
e.Cancel = true;
return;
}
After everyline in my Backgroundworker_DoWork but it's so stupid and when i get Thread.Sleep(10000); it gonna takes 10 sec...
Is any way to just kill instantly my background worker?
Thanks for help!
I think that standard BackgroundWorker is not suitable for your case and you should do something custom that better support combination of sleep and cancellation. Following code is an idea of what you might want to do:
CancellableBackgroundWorker.cs
This is a class similar to standard BackgroundWorker but providing some callbacks for your goal (see ICancellationProvider and FinishedEvent).
public delegate void CancellableBackgroundJob(ICancellationProvider cancellation);
public interface ICancellationProvider
{
bool CheckForCancel();
void CheckForCancelAndBreak();
void SleepWithCancel(int millis);
}
public class CancellableBackgroundWorker : Component, ICancellationProvider
{
private readonly ManualResetEvent _canceledEvent = new ManualResetEvent(false);
private readonly CancellableBackgroundJob _backgroundJob;
private volatile Thread _thread;
private volatile bool _disposed;
public EventHandler FinishedEvent;
public CancellableBackgroundWorker(CancellableBackgroundJob backgroundJob)
{
_backgroundJob = backgroundJob;
}
protected override void Dispose(bool disposing)
{
Cancel();
_disposed = true;
}
private void AssertNotDisposed()
{
if (_disposed)
throw new InvalidOperationException("Worker is already disposed");
}
public bool IsBusy
{
get { return (_thread != null); }
}
public void Start()
{
AssertNotDisposed();
if (_thread != null)
throw new InvalidOperationException("Worker is already started");
_thread = new Thread(DoWorkWrapper);
_thread.Start();
}
public void Cancel()
{
AssertNotDisposed();
_canceledEvent.Set();
}
private void DoWorkWrapper()
{
_canceledEvent.Reset();
try
{
_backgroundJob(this);
Debug.WriteLine("Worker thread completed successfully");
}
catch (ThreadAbortException ex)
{
Debug.WriteLine("Worker thread was aborted");
Thread.ResetAbort();
}
finally
{
_canceledEvent.Reset();
_thread = null;
EventHandler finished = FinishedEvent;
if (finished != null)
finished(this, EventArgs.Empty);
}
}
#region ICancellationProvider
// use explicit implementation of the interface to separate interfaces
// I'm too lazy to create additional class
bool ICancellationProvider.CheckForCancel()
{
return _canceledEvent.WaitOne(0);
}
void ICancellationProvider.CheckForCancelAndBreak()
{
if (((ICancellationProvider)this).CheckForCancel())
{
Debug.WriteLine("Cancel event is set, aborting the worker thread");
_thread.Abort();
}
}
void ICancellationProvider.SleepWithCancel(int millis)
{
if (_canceledEvent.WaitOne(millis))
{
Debug.WriteLine("Sleep aborted by cancel event, aborting the worker thread");
_thread.Abort();
}
}
#endregion
}
The main trick is to use ManualResetEvent.WaitOne instead of Thread.Sleep for sleeping. With such approach working thread might be safely woken up (for cancellation) from a different (UI) thread. Another trick is to use ThreadAbortException via Thread.Abort to enforce quick end of the background thread execution (and don't forget about Thread.ResetAbort at the end of stack unwinding).
You may use this class as following:
public partial class Form1 : Form
{
private readonly CancellableBackgroundWorker _backgroundWorker;
public Form1()
{
InitializeComponent();
_backgroundWorker = new CancellableBackgroundWorker(DoBackgroundJob);
_backgroundWorker.FinishedEvent += (s, e) => UpdateButton();
// ensure this.components is created either by InitializeComponent or by us explicitly
// so we can add _backgroundWorker to it for disposal
if (this.components == null)
this.components = new System.ComponentModel.Container();
components.Add(_backgroundWorker);
}
private void UpdateButton()
{
// Ensure we interact with UI on the main thread
if (InvokeRequired)
{
Invoke((Action)UpdateButton);
return;
}
button1.Text = _backgroundWorker.IsBusy ? "Cancel" : "Start";
}
private void button1_Click(object sender, EventArgs e)
{
if (_backgroundWorker.IsBusy)
{
_backgroundWorker.Cancel();
}
else
{
_backgroundWorker.Start();
}
UpdateButton();
}
private void DoBackgroundJob(ICancellationProvider cancellation)
{
Debug.WriteLine("Do something");
// if canceled, stop immediately
cancellation.CheckForCancelAndBreak();
Debug.WriteLine("Do something more");
if (cancellation.CheckForCancel())
{
// you noticed cancellation but still need to finish something
Debug.WriteLine("Do some necessary clean up");
return;
}
// Sleep but cancel will stop and break
cancellation.SleepWithCancel(10000);
Debug.WriteLine("Last bit of work");
}
}
Now i use a method that update all the time when connection event is raised, but now for connection i use a different thread an i have problem to call that event from Icommand thread i get an error System.StackOwverflowException, i read on internet bout this problem and this problem i think cam solved with Invoker but i do not understand the concept of invoker how to use it.
My code:
public class NewMeasurementCommand : ICommand
{
private MeasurementViewModel measurementViewModel = null;
private BaseViewModel baseViewModel;
private GpfGateway gpfGateway;
public NewMeasurementCommand(MeasurementViewModel viewModel)
{
measurementViewModel = viewModel;
GpfGateway.GetInstance().SystemStatus += updateCanExecuteChanged;
}
/// <summary>Notifies command to update CanExecute property.</summary>
private void updateCanExecuteChanged(object sender, EventArgs e)
{
updateCanExecuteChanged(sender, new EventArgs());
}
bool ICommand.CanExecute(object parameter)
{
return GpfGateway.GetInstance().IsConnected;
}
public event EventHandler CanExecuteChanged;
void ICommand.Execute(object parameter)
{
NewMeasurementViewModel newMeasurementViewModel = new NewMeasurementViewModel();
measurementViewModel.MeasurementModel.MeasurementStep = new MeasurementInfoStep();
measurementViewModel.MeasurementModel.MeasurementStep.NewMeasurementVM = newMeasurementViewModel;
GpfGateway.GetInstance().ControllerValuesArrived += measurementViewModel.MeasurementModel.MeasurementStep.RemoteControllerArrived;
newMeasurementViewModel.MeasurementModel = measurementViewModel.MeasurementModel;
newMeasurementViewModel.MeasurementModel.CurrentMeasurement = new Measurement();
measurementViewModel.MeasurementModel.MeasurementStep.CurrentMeasurement = newMeasurementViewModel.MeasurementModel.CurrentMeasurement;
newMeasurementViewModel.NavigationResolver = measurementViewModel.NavigationResolver;
measurementViewModel.MeasurementModel.CurrentMeasurement = new Measurement();
measurementViewModel.MeasurementModel.MeasurementStep.CurrentMeasurement = measurementViewModel.MeasurementModel.CurrentMeasurement;
measurementViewModel.MeasurementModel.CurrentMeasurement.Tester = Environment.UserName;
measurementViewModel.NavigationResolver.GoToMeasurementInfoStep(newMeasurementViewModel);
}
private void updateCanExecuteChanged(object sender, NotifyCollectionChangedEventArgs e)
{
CanExecuteChanged(this, new EventArgs());
}
}
}
What I try to make:
public delegate void InvokeDelegate();
private void EnabledChanged(object sender, EventArgs e)
{
this.BeginInvoke((MethodInvoker)delegate
{
EnabledChanged();
});
if(sender == gpfGateway.IsConnected);
}
If anyone have some advice it will be very helpful.
You're getting a stack overflow because your EnabledChanged function calls itself. So its just going round and round recalling itself until it goes boom.
If you look at Microsofts invoke
You'll see they dont call the function from itself, but from somewhere else.
What you can do is something like this
private void UpdateStatus(String message)
{
if (this.InvokeRequired)
this.Invoke((MethodInvoker)delegate
{
UpdateStatus(message);
});
else
label1.Text = message;
}
While this is setting text on a label, its still a reasonable example. Any GUI element cannot be played with from another thread, so, you can use a function such as this from anywhere, if it needs to it then invokes the command. You can have it call itself, in this instance, because after invoking it wont need to invoke itself again.
Uisng Visual Studio 2008.
The main form is subscribing to an event in a class in order to report progress.
The ReportProgress event in the CSVReader class is ALWAYS coming up null and I just can't seem to see why this is.
Main Form:
//Constructor
public CreateSQL()
{
InitializeComponent();
csvReader = new CSVReader();
}
private void btnCreateSQL_Click(object sender, EventArgs e)
{
if (backgroundWorker1.IsBusy != true)
{
backgroundWorker1.ProgressChanged += backgroundWorker1_ProgressChanged;
backgroundWorker1.RunWorkerCompleted += backgroundWorker1_RunWorkerCompleted;
**csvReader.ReportProgress += new EventHandler<CSVReader.ProgressArgs>(CSVReader_ReportProgress);**
// Start the asynchronous operation.
backgroundWorker1.RunWorkerAsync();
}
}
protected void CSVReader_ReportProgress(object sender, CSVReader.ProgressArgs e)
{
// Call the UI backgroundworker
backgroundWorker1.ReportProgress(e.Percentage, e.Message);
}
private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
DataTable dt = csvReader.ReadCSVFile(sFile, _hasHeader);
}
And the Class CSVReader:
public class CSVReader : IDisposable
{
// Event handler to bind to for reporting progress
public EventHandler<ProgressArgs> ReportProgress;
// Eventargs to contain information to send to the subscriber
public class ProgressArgs : EventArgs
{
public int Percentage { get; set; }
public string Message { get; set; }
}
}
public CSVReader()
{
}
public DataTable ReadCSVFile(string filename, bool headerRow)
{
using (CSVReader reader = new CSVReader(new FileInfo(filename)))
return reader.CreateDataTable(headerRow);
}
public DataTable CreateDataTable(bool headerRow)
{
// Read the CSV data into rows
List<List<object>> rows = new List<List<object>>();
List<object> readRow = null;
while ((readRow = ReadRow()) != null)
rows.Add(readRow);
// Report progress if somebody is listening (subscribed)
**if (ReportProgress != null)
{
ReportProgress(this, new ProgressArgs { Percentage = 33, Message = "Reading File" });
}**
}
The ReportProgress event is tested above if it's null and it is always is null.
I placed it here just for a test to get it sending back a couple variables, 33 and a string, but it's always null.
Thanks for any and all input!
I have a producer-consumer class as following.
public class ProducerConsumer<T> where T : class
{
private Thread _workerThread;
private readonly Queue<T> _workQueue;
private readonly object _lockObject = new object();
private readonly Action<T> _workCallbackAction;
private ManualResetEvent _workerWaitSignal;
public ProducerConsumer(Action<T> action)
{
_workCallbackAction = action;
_workQueue = new Queue<T>();
}
private void DoWork()
{
while (true)
{
T workItemToBeProcessed = default(T);
bool hasSomeWorkItem = false;
lock (_lockObject)
{
hasSomeWorkItem = _workQueue.Count > 0;
if (hasSomeWorkItem)
{
workItemToBeProcessed = _workQueue.Dequeue();
if (workItemToBeProcessed == null)
{
return;
}
}
}
if (hasSomeWorkItem)
{
if (_workCallbackAction != null)
{
_workCallbackAction(workItemToBeProcessed);
}
}
else
{
_workerWaitSignal.WaitOne();
Debug.WriteLine("Waiting for signal.");
}
}
}
public void EnQueueWorkItem(T workItem)
{
lock (_lockObject)
{
_workQueue.Enqueue(workItem);
_workerWaitSignal.Set();
}
}
public void StopWork(ManualResetEvent stopSignal)
{
EnQueueWorkItem(null);
_workerThread.Join();
_workerWaitSignal.Close();
_workerWaitSignal = null;
if (stopSignal != null)
{
stopSignal.Set();
}
}
public void ReStart()
{
_workerWaitSignal = new ManualResetEvent(false);
_workerThread = new Thread(DoWork) { IsBackground = true };
_workerThread.Start();
}
}
and i am using this in the following way:
public partial class Form1 : Form
{
private RecordProducerConsumer<string> _proConsumer;
public Form1()
{
InitializeComponent();
_proConsumer = new RecordProducerConsumer<string>(DoAction);
}
private bool restart=true;
private int item = 0;
private void button1_Click(object sender, EventArgs e)
{
if (restart)
{
_proConsumer.ReStart();
restart = false;
}
item++;
_proConsumer.EnQueueWorkItem(item.ToString());
}
private void DoAction(string str)
{
Debug.WriteLine(str);
}
private void btnStop_Click(object sender, EventArgs e)
{
ManualResetEvent mre = new ManualResetEvent(false);
_proConsumer.StopWork(mre);
mre.WaitOne();
restart = true;
}
private void Stop(ManualResetEvent mre)
{
mre.WaitOne();
}
}
My problem or what I can not understand is when I click Start button I am adding only one item and it Dequeue that item but keeps on running the loop so I see lot of "Waiting for signal." print outs on the Output window in Visual Studio.
Why does it not stop on _workerWaitSignal.WaitOne(); in DoWork() method , why is it running all the time ?
Couple of issues:
It makes hardly any sense to output 'Waiting for issue' after executing the wait. Consider moving the write before the actual wait.
You are using a ManualResetEvent — as its name indicates, it requires a manual reset to revert from the signalled state. However, I can't see a call to Reset in your code.
To avoid other concurrency issues (e.g. a race condition when when resetting the event while other thread set the event after enqueuing another work item), consider using a Semaphore for your scenario instead.
try this... I could be wrong...but that is all i could figure out by reading through your code. Hope this helps :)
private void button1_Click(object sender, EventArgs e)
{
if (restart)
{
restart = false;
_proConsumer.ReStart();
}
item++;
_proConsumer.EnQueueWorkItem(item.ToString());
}
I haven't read the code thoroughly, but I can venture a guess that you meant to use an AutoResetEvent (which resets automatically after some WaitOne() is released) rather than a ManualResetEvent (which stays set until you explicitly call Reset()).
Also, is there any reason you're not using .NET's BlockingCollection<T> ? It's the framework implementation of the producer/consumer pattern, and it works very well.