However, i have now run into the issue where i need to change a WinForms control append a string to textbox from a thread that was initiated in a different class. I have searched around, and found solutions for different threads, and in different classes, but not both and the solutions provided seem incompatible to me. This may be the biggest 'lead' however: How to update UI from another thread running in another class.
I understand that eventhandlers are probably the way to go, but i can't work out how to do so in this situation I am also open to other suggestions ;. It does not matter from which class you are updating the form. WinForm controls have to be updated on the same thread that they were created on.
Hence, Control. Invoke, allows you to execute a method on the control on its own thread. This is also called asynchronous execution, since the call is actually queued up and executed separately. Look at this article from msdn , the example is similar to your example.
A separate class on a separate thread updates a list box on the Form. How are we doing? Please help us improve Stack Overflow.
Take our short survey. In the timer section of Form2 use Form1. Text to update it. I am using the old instance of the form1 to retrive its values. It is working for me right now. But I am looking for a solution which uses "observer patterns" for the same job. Thank you Amit. But getting an error "Invoker" 3rd line of code could not be found.
If you do need to update a form from another thread, I recommend using BackgroundWorker instead of Thread directly. It has synchronization built-in through its events. Context seeblunt Dec Thinking about threads running in the context of a form or control doing work possibly using UI properties then setting UI properties or calling Functions that set UI properties this is a very elegant solution.
I have modified it a little based on my observations of thread usage within such context. I have deliberately confined to usage on Control derived classes to clarify usage. TResult isi. InvokeRequired isi. Text ; this. Show Thread. My vote of 5 Omar Gameel Salem 1-Nov Omar Gameel Salem. Works extremely well!
I've written several programs that had to deal with updating from a back-ground task. I always dread making all the special routines, this solution worked beautifully! It's wonderful! I don't understand how it works , but I don't care! James Maeding. I am a beginner at threading. EndInvoke result ; return TResult endResult; if the calc is running. What is the way to handle this? I added a done button to the form with form. Re: demo prog gives error when form closed Michael Demeersseman Dec It's also wise to set the IsBackground property of the thread object to true.
That way you prevent that the thread still runs even when the form has closed. All background threads are automatically closed when no non-background thread are active anymore. Why not use Invoke?
Re: Why not use Invoke? Your simplification works for me, does anyone see any drawbacks? Regards, John. The difference between Control. Invoke and Control. When the asynchronous action is scheduled, your code continues. Some time later you don't know exactly when your asynchronous action will be executed. A logical conclusion is that a delegate you pass to Invoke can have out-parameters or a return-value, while a delegate you pass to BeginInvoke cannot you have to use EndInvoke to retrieve the results.
My advice is: always use BeginInvoke if you can. Imagine that your application has a dedicated worker thread that uses Invoke to execute some work on the GUI thread. Now image that during this work, your GUI code needs to execute something on the worker-thread.
It will be blocked forever because your worker-thread is already busy waiting for your GUI-thread. In this simple example it might be easy to spot the problem. In a big application developed by many people it will not always be this easy. Therefore it is better to find a pattern that avoids blocking altogether.
Note that in this example you might think that a threadpool solves your problem, because then you have multiple workerthreads. However the problem will still occur under high load, this is called threadpool starvation and it is a very complex problem.
ProgressChanged and BackgroundWorker. RunWorkerCompleted event handlers, which can call the main thread's controls. To make a thread-safe call by using BackgroundWorker , handle the DoWork event. There are two events the background worker uses to report status: ProgressChanged and RunWorkerCompleted.
The ProgressChanged event is used to communicate status updates to the main thread, and the RunWorkerCompleted event is used to signal that the background worker has completed its work. To start the background thread, call BackgroundWorker. The example counts from 0 to 10 in the DoWork event, pausing for one second between counts. It uses the ProgressChanged event handler to report the number back to the main thread and set the TextBox control's Text property.
For the ProgressChanged event to work, the BackgroundWorker. WorkerReportsProgress property must be set to true. Skip to main content. This browser is no longer supported. Download Microsoft Edge More info. Contents Exit focus mode. How to make thread-safe calls to controls Windows Forms.
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