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how to notify method that something is done

My constructor besides other things call another method DoWork
public MyTask(TaskAction action)
{
DoWork(action);
}
DoWork method goes to another method Calc(2)
private void Calc (int 2){
... calc and save result into file
}
How can I alert MyTask that Calc is done and let MyTask to continue further.
P.S. I could read hdd every few secs in order to see whether file with result is save and based on that continue further, but I assume that there is better way.

BackgroundWorker class allows you to easily manage your async work.
BackgroundWorker _worker = new BackgroundWorker();
public Cnt()
{
InitializeComponent();
_worker.DoWork += WorkerOnDoWork;
_worker.RunWorkerCompleted += WorkerOnRunWorkerCompleted;
//start your work
_worker.RunWorkerAsync();
}
private void WorkerOnRunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
//Worker completed event
}
private void WorkerOnDoWork(object sender, DoWorkEventArgs e)
{
//Do
}

There are many ways to do this.The latest recommended is using tasks
Task taskA = new Task(() => { Console.WriteLine("Task A started"); });
taskA.ContinueWith((ss) => { Console.WriteLine("Task A finished"); });
taskA.Start();
http://msdn.microsoft.com/en-us/library/ee372288(v=vs.110).aspx
This way you can block the current thread if you want.
Another way is the BackGroundWorker Class
Also, you can use a custom callback like this
using System;
namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
DoWorkA(DoWorkFinished);
Console.Read();
}
private static void DoWorkA(Action whatToDoWhenFinished)
{
Console.WriteLine("Doing something");
whatToDoWhenFinished();
}
private static void DoWorkFinished()
{
Console.WriteLine("Doing something Else");
}
}
}

Passing custom object to RunWorkerCompleted event in case of an exception

My Console App uses System.ComponentModel.BackgroundWorker for threading purposes:
System.ComponentModel.BackgroundWorker backgroundWorker = new System.ComponentModel.BackgroundWorker();
backgroundWorker.DoWork += (sender, e) =>
ReportStatus(worker, status, result, e);
backgroundWorker.RunWorkerCompleted += new System.ComponentModel.RunWorkerCompletedEventHandler(backgroundWorker1_RunWorkerCompleted);
backgroundWorker.RunWorkerAsync(worker);
As you can see that I am passing "worker" as an argument inside RunWorkerAsync.
What I am trying to achieve is that if there is an exception inside ReportStatus method I need the same "worker" object so that I can perform some operation (Call a service to notify that workers exception)
private void ReportStatus(Worker worker, Status status, WorkResult result,System.ComponentModel.DoWorkEventArgs arg)
{
var proxy = new PreparationServiceProxy(new NetTcpBinding(), new EndpointAddress(PreparationEngineState.ServiceAddress));
try
{
proxy.ReportStatus(worker, status, result);
proxy.Close();
}
catch (Exception)
{
arg.Result = worker;
proxy.Abort();
throw;
}
}
In my exception block (I am not sure if this is the correct way!) I am assigning the worker to the Result so that I can get the same worker back when the RunWorkerCompleted method (backgroundWorker1_RunWorkerCompleted) is executed :
private void backgroundWorker1_RunWorkerCompleted(object sender, System.ComponentModel.RunWorkerCompletedEventArgs e)
{
if (e.Error != null)
{
Worker worker = e.Result as Worker; // At this point I get an exception!
}
}

It's because you re-threw the exception. BackgroundWorker sees that as an exception unhandled by the DoWork handler and re-throws it back on the other thread when you get the Result value.
If you don't want it to do that, remove the throw in your catch in the DoWork handler.
if you passed the worker object into the BackgroundWorker, why don't use just use what you passed in in an exception handler wrapping the call to Result or in the block that tests Error? e.g.:
if (e.Error != null)
{
worker.DoSomething(); // no access of Result
}

.NET does NOT consider that Async Operation might have some result if an Error happened. That's why you will have pass it some other way.
I would recommend to implement custom exception class:
public class WorkerException:ApplicationException
{
public WorkerException(Worker worker,Exception innerException):base(null,innerException)
{ Worker = worker; }
public Worker Worker
{
get;
set;
}
}
And wrap you exception accordingly:
private void ReportStatus(Worker worker, Status status, WorkResult result,System.ComponentModel.DoWorkEventArgs arg)
{
var proxy = new PreparationServiceProxy(new NetTcpBinding(), new EndpointAddress(PreparationEngineState.ServiceAddress));
try
{
proxy.ReportStatus(worker, status, result);
proxy.Close();
}
catch (Exception exception)
{
arg.Result = worker;
proxy.Abort();
throw new WorkerException(worker,exception);
}
}
In this case you will be able to retrieve Worker of exception, casting Error to WorkerException:
private void backgroundWorker1_RunWorkerCompleted(object sender, System.ComponentModel.RunWorkerCompletedEventArgs e)
{
if (e.Error is WorkerException)
{
Worker worker = ((WorkerException)e.Error).Worker; // At this point I get an exception!
}
}

The RunWorkerCompletedEventArgs contains a UserState property which (I think) should be a reference to the same object that you passed to the RunWorkerAsync method. (It should also be in the DoWorkEventArgs as the Argument property.)
You'll need to experiment to confirm that this UserState is the right object (cast it as Worker) and that it is valid even when the DoWork handler threw an exception, but I think that could be what you're looking for.

Exception handler not being invoked

Running the really simple program below I'd expect 'FILTER REACHED' to execute when I click button1, but it doesn't get hit (neither with nor without debugger attached). Any ideas ... ?
public partial class Window1 : Window
{
public Window1()
{
InitializeComponent();
}
private void button1_Click(object sender, RoutedEventArgs e)
{
new Thread(() =>
{
Dispatcher.CurrentDispatcher.UnhandledExceptionFilter += Dispatcher_UnhandledExceptionFilter;
doer();
}).Start();
}
void Dispatcher_UnhandledExceptionFilter(
object sender,
DispatcherUnhandledExceptionFilterEventArgs e)
{
MessageBox.Show("FILTER REACHED");
}
private void doer()
{
throw new NotImplementedException();
}
}
Thanks

According to the documentation on Dispatcher (found here) it looks like the filter function will only be used if an uncaught exception is raised from the Invoke or BeginInvoke methods on the Dispatcher.
So what happens if you replace doer() with Dispatcher.CurrentDispatcher.Invoke(doer) (or similar) instead?

You are calling the method (doer) from a thread which is not the dispatcher thread.. you have to invoke the method using Dispatcher in order to catch the exception for filtering.
new Thread(() =>
{
Dispatcher.CurrentDispatcher.UnhandledExceptionFilter += Dispatcher_UnhandledExceptionFilter;
Dispatcher.Invoke(new Action(()=>doer()));
}).Start();

try below code
new Thread(() =>
{
Dispatcher.CurrentDispatcher.UnhandledExceptionFilter += Dispatcher_UnhandledExceptionFilter;
Dispatcher.CurrentDispatcher.Invoke(DispatcherPriority.Normal, new ThreadStart(delegate
{
doer();
}));
}).Start();

Have you tried using AppDomain.UnhandledException instead?

Question on threading in C#

I have a Windows Forms application at the moment, and I want to create a new thread and run a method on another class that accepts an input.
For example
public partial class Form1: Form {
SerialPort serialInput;
// I want to create a new thread that will pass the parameter serialInput into the method
// SMSListener on another class and run the method contionously on the background.
}
class SMS
{
public void SMSListener(SerialPort serial1)
{
serial1.DataReceived += port_DataRecieved;
}
private void port_DataRecieved(object sender, SerialDataReceivedEventArgs e)
{
// Other codes
}
}
How do I perform this in C#? I have seen numerous examples on the web, and most of them run the method on the same class with no parameters, but none that suits my requirements.

Perhaps a Background Worker could help you?
It is a bit hard to understand what you are aiming at.
public class Runner
{
private readonly BackgroundWorker _worker = new BackgroundWorker();
public Runner()
{
_worker.DoWork += WorkerDoWork;
}
public void RunMe(int payload)
{
_worker.RunWorkerAsync(payload);
}
static void WorkerDoWork(object sender, DoWorkEventArgs e)
{
var worker = sender as BackgroundWorker;
while (true)
{
if (worker.CancellationPending)
{
e.Cancel = true;
break;
}
// Work
System.Threading.Thread.Sleep((int)e.Argument);
}
}
}

I am not an expert on Multithreading but to the best of my knowledge you can only start threads on methods that accept an object parameter and return void. So in order to achieve that for your problem (don't shoot me down if there is a better approach!) I would do something like
public partial class Form1: Form {
SerialPort serialInput;
// I want to create a new thread that will pass the parameter serialInput into the method
// SMSListener on another class and run the method contionously on the background.
SMS sms = new SMS();
Thread t = new Thread(sms.SMSListenerUntyped);
t.Start(serialInput);
}
class SMS
{
public void SMSListenerUntyped(object serial1) {
if (serial1 is SerialPort) //Check if the parameter is correctly typed.
this.SMSListener(serial1 as SerialPort);
else
throw new ArgumentException();
}
public void SMSListener(SerialPort serial1)
{
serial1.DataReceived += port_DataRecieved;
}
private void port_DataRecieved(object sender, SerialDataReceivedEventArgs e)
{
// Other code.
}

How about just use the ThreadPool directly with a anonymous method allowing you to access your surrounding locals?
public void OnButtonClick(object sender, EventArgs e)
{
SerialPort serialInput = this.SerialInput;
System.Threading.ThreadPool.QueueUserWorkItem(delegate
{
SmsListener listener = new SmsListener(serialInput);
});
}

How do I make event callbacks into my win forms thread safe?

When you subscribe to an event on an object from within a form, you are essentially handing over control of your callback method to the event source. You have no idea whether that event source will choose to trigger the event on a different thread.
The problem is that when the callback is invoked, you cannot assume that you can make update controls on your form because sometimes those controls will throw an exception if the event callback was called on a thread different than the thread the form was run on.

To simplify Simon's code a bit, you could use the built in generic Action delegate. It saves peppering your code with a bunch of delegate types you don't really need. Also, in .NET 3.5 they added a params parameter to the Invoke method so you don't have to define a temporary array.
void SomethingHappened(object sender, EventArgs ea)
{
if (InvokeRequired)
{
Invoke(new Action<object, EventArgs>(SomethingHappened), sender, ea);
return;
}
textBox1.Text = "Something happened";
}

Here are the salient points:
You can't make UI control calls from a different thread than the one they were created on (the form's thread).
Delegate invocations (ie, event hooks) are triggered on the same thread as the object that is firing the event.
So, if you have a separate "engine" thread doing some work and have some UI watching for state changes which can be reflected in the UI (such as a progress bar or whatever), you have a problem. The engine fire's an object changed event which has been hooked by the Form. But the callback delegate that the Form registered with the engine gets called on the engine's thread… not on the Form's thread. And so you can't update any controls from that callback. Doh!
BeginInvoke comes to the rescue. Just use this simple coding model in all your callback methods and you can be sure that things are going to be okay:
private delegate void EventArgsDelegate(object sender, EventArgs ea);
void SomethingHappened(object sender, EventArgs ea)
{
//
// Make sure this callback is on the correct thread
//
if (this.InvokeRequired)
{
this.Invoke(new EventArgsDelegate(SomethingHappened), new object[] { sender, ea });
return;
}
//
// Do something with the event such as update a control
//
textBox1.Text = "Something happened";
}
It's quite simple really.
Use InvokeRequired to find out if this callback happened on the correct thread.
If not, then reinvoke the callback on the correct thread with the same parameters. You can reinvoke a method by using the Invoke (blocking) or BeginInvoke (non-blocking) methods.
The next time the function is called, InvokeRequired returns false because we are now on the correct thread and everybody is happy.
This is a very compact way of addressing this problem and making your Forms safe from multi-threaded event callbacks.

I use anonymous methods a lot in this scenario:
void SomethingHappened(object sender, EventArgs ea)
{
MethodInvoker del = delegate{ textBox1.Text = "Something happened"; };
InvokeRequired ? Invoke( del ) : del();
}

I'm a bit late to this topic, but you might want to take a look at the Event-Based Asynchronous Pattern. When implemented properly, it guarantees that events are always raised from the UI thread.
Here's a brief example that only allows one concurrent invocation; supporting multiple invocations/events requires a little bit more plumbing.
using System;
using System.ComponentModel;
using System.Threading;
using System.Windows.Forms;
namespace WindowsFormsApplication1
{
public class MainForm : Form
{
private TypeWithAsync _type;
[STAThread()]
public static void Main()
{
Application.EnableVisualStyles();
Application.Run(new MainForm());
}
public MainForm()
{
_type = new TypeWithAsync();
_type.DoSomethingCompleted += DoSomethingCompleted;
var panel = new FlowLayoutPanel() { Dock = DockStyle.Fill };
var btn = new Button() { Text = "Synchronous" };
btn.Click += SyncClick;
panel.Controls.Add(btn);
btn = new Button { Text = "Asynchronous" };
btn.Click += AsyncClick;
panel.Controls.Add(btn);
Controls.Add(panel);
}
private void SyncClick(object sender, EventArgs e)
{
int value = _type.DoSomething();
MessageBox.Show(string.Format("DoSomething() returned {0}.", value));
}
private void AsyncClick(object sender, EventArgs e)
{
_type.DoSomethingAsync();
}
private void DoSomethingCompleted(object sender, DoSomethingCompletedEventArgs e)
{
MessageBox.Show(string.Format("DoSomethingAsync() returned {0}.", e.Value));
}
}
class TypeWithAsync
{
private AsyncOperation _operation;
// synchronous version of method
public int DoSomething()
{
Thread.Sleep(5000);
return 27;
}
// async version of method
public void DoSomethingAsync()
{
if (_operation != null)
{
throw new InvalidOperationException("An async operation is already running.");
}
_operation = AsyncOperationManager.CreateOperation(null);
ThreadPool.QueueUserWorkItem(DoSomethingAsyncCore);
}
// wrapper used by async method to call sync version of method, matches WaitCallback so it
// can be queued by the thread pool
private void DoSomethingAsyncCore(object state)
{
int returnValue = DoSomething();
var e = new DoSomethingCompletedEventArgs(returnValue);
_operation.PostOperationCompleted(RaiseDoSomethingCompleted, e);
}
// wrapper used so async method can raise the event; matches SendOrPostCallback
private void RaiseDoSomethingCompleted(object args)
{
OnDoSomethingCompleted((DoSomethingCompletedEventArgs)args);
}
private void OnDoSomethingCompleted(DoSomethingCompletedEventArgs e)
{
var handler = DoSomethingCompleted;
if (handler != null) { handler(this, e); }
}
public EventHandler<DoSomethingCompletedEventArgs> DoSomethingCompleted;
}
public class DoSomethingCompletedEventArgs : EventArgs
{
private int _value;
public DoSomethingCompletedEventArgs(int value)
: base()
{
_value = value;
}
public int Value
{
get { return _value; }
}
}
}

As the lazy programmer, I have a very lazy method of doing this.
What I do is simply this.
private void DoInvoke(MethodInvoker del) {
if (InvokeRequired) {
Invoke(del);
} else {
del();
}
}
//example of how to call it
private void tUpdateLabel(ToolStripStatusLabel lbl, String val) {
DoInvoke(delegate { lbl.Text = val; });
}
You could inline the DoInvoke inside your function or hide it within separate function to do the dirty work for you.
Just keep in mind you can pass functions directly into the DoInvoke method.
private void directPass() {
DoInvoke(this.directInvoke);
}
private void directInvoke() {
textLabel.Text = "Directly passed.";
}

In many simple cases, you can use the MethodInvoker delegate and avoid the need to create your own delegate type.