Windows cross thread communication

RunWorkerCompleted when the task is over, to notify the UI thread. ToString e. Sleep ; e. Put a break point in th DoWork event handler and RunWorkerCompleted event handler: So how do we confirm what I said above: run the code with debugger F5 : when the breakpoint is hit, open the "Threads" window from your devenv and you will see that the cursor at "Worker Thread" in the category column and just above that you will see the "Main Thread" i.

Now let us hit F5 and let the debugger reach the RunWorkerCompleted event handler where we have set another debug point and inspect the "Threads" window again:. The arrow now points back to the "Main thread" indicating that the call is marshaled back to the UI thread i.

So you see that the BackgroundWorker Class internally takes care of marshaling the requests back to the UI threads. I will urge the readers to go ahead and try to access any UI control in DoWork event handlers to see the "Cross thread exceptions" being thrown that will give them understanding of why we had to do this.

View All. If you set the flags to be background threads, then they will not keep the application alive, but also not tie up a thread pool thread as well as keep your intention clear :. LongRunning ;. This uses the TPL to handle this, but specifies that this is a "long running" task to prevent using a ThreadPool thread, with the default TaskScheduler.

Once I have created a background thread, how do I pass the data to the main thread from this background thread? It's all in one process. You can access the data from any thread just synchronize it. Your code should work the same way it did when you used the ThreadPool That being said, since you're effectively polling, you might want to consider just using a Windows Forms Timer on your form, and check in the timer's Tick event on regular intervals.

This will simplify the design of your application tremendously I still had one query. In most of the articles I read, the main thread was creating a worker thread from Thread Pool, and any cross thread communication between worker thread and main thread was happening by using a delegate.

So is it so that if I were to use threads from thread pool, I have to use a delegate and if I want to communicate between foreground and background threads in the same process, then I don't need a delegate? You need to use a delegate if you want to do something with the user interface from within a background thread. Invoke or Control. That being said, as John and I both mentioned - consider using a Windows.

Timer instead - it would simplify this, and eliminate the need for threads I have understood your point clearly. I have to display an image on a button if I recieve a message from any one of the hubs. You have also mentioned about Windows. Timer, so will this be useful in my scenario as I have two hubs to listen to throughout application life time. Do you mean that using timer, I listen to these hubs alternatively for messages on tick event? In this case, I will have to check for messages from the main thread windows forms thread on time tick event, so will this not make main form unresponsive for the duration it checks for messages and since I am going to poll for messages throughout application life time, will this not have any impact on the responsiveness of the main form?

Hello patelmahesh, you can use two timers or only one , but threading timers, not WinForm timers. For example, create a new Windows Forms Application Project, add a text box and replace the code behind of the Form1 class with this one:.

I have to continuously poll for messages on a queue on a different server. I will have to poll for the lifetime of the application. The content you requested has been removed. Ask a question. Quick access. Search related threads. Remove From My Forums. Answered by:. The idea in this pattern is that you create one EventAggregator for each of your views but the EventAggregator contains a static shared list of subscribers which are common to all the views. InitializeComponent ; this. You can get around the problem using CoreDispatcher.

EventAggregator is one example of this kind of a pattern.