WPF: How to do multithreading in a given situation where I need to check control's state

Question

Here's my situation:

I have a WPF application, where I have a method which takes a lot of time to be completed. I don't want to lose UI responsiveness, so I'd like to call that method in another thread. I won't paste here my entire code, because it's too long, instead I wrote this short program, which represents well what I'm dealing with:

    public void MainWindow()
    {
        InitializeComponent();

        ProcessThread = new Thread(TimeConsumingMethod);
        ProcessThread.Name = "ProcessThread";
        ProcessThread.Start();

    }


    public void TimeConsumingMethod()
    {
        this.Dispatcher.Invoke(() =>
        {
            MytextBlock.Text = "new text";
            MyOtherTextBlock.Text = "Hello";
        });

        for (int i = 0; i < 50; i++)
        {
            Debug.WriteLine("Debug line " + i);
        }


        if (MyRadioButton.IsChecked == false)   //????????????????
        {
            while (true)
            {
                if (DateTime.Now >= timePicker.Value)
                    break;
            }
        }

        OtherMethod();

    }

Actually, I have two questions for the above code: 1. Everytime I want to access UI controls in my code I have to use this.Dispatcher.Invoke() =>.... Is it the right thing to do? I mean, I have a few places in my method (in my real code) where I check the state of some controls and everytime I need to do his Dispatcher.invoke thing - isn't there a better way to acces these controls? 2. In the code above, there's IF block in the end - in that block I'm checking the state of my RadioButton. Inside of that IF, I have a time consuming code. I cannot just do this:

    this.Dispatcher.Invoke(() =>
    {
        if (MyRadioButton.IsChecked == false)   //????????????????
        {
            while (true)
            {
                if (DateTime.Now >= timePicker.Value)
                    break;
            }
        }
    });

That code would tell my UI thread to handle this if block - but I don't want that! That would cause the whole UI to freeze until this IF block gets done. How should I handle this situation?

Answer 1

Well, there are a lot of ways to implement what you are trying to do. One of them might look like this:

    public MainWindow() {
        InitializeComponent();
        Initialize(); //do some intialization
    }

    private async void Timer_Tick(object sender, EventArgs e) {
        if (DateTime.Now >= timePicker.SelectedDate) { //check your condition
            timer.Stop(); //probably you need to run it just once

            await Task.Run(() => OtherMethod()); //instead of creating thread manually use Thread from ThreadPool
            //use async method to avoid blocking UI during long method is running
        }
    }

    private readonly DispatcherTimer timer = new DispatcherTimer(); //create a dispatcher timer that will execute code on UI thread

    public void Initialize() {
        MytextBlock.Text = "new text";
        MyOtherTextBlock.Text = "Hello"; //access UI elements normally

        for (var i = 0; i < 50; i++) {
            Debug.WriteLine("Debug line " + i);
        }

        if (MyRadioButton.IsChecked == false)
        {
            timer.Interval = TimeSpan.FromSeconds(10); // during init setup timer instead of while loop
            timer.IsEnabled = true;
            timer.Tick += Timer_Tick; //when 10 sec pass, this method is called
            timer.Start();
        }
    }

    public void OtherMethod() {
        //long running method
        Thread.Sleep(1000);
    }

I've added some comments, but the main idea is this:

1. Don't create threads manually, use ThreadPool

2. Don't loop to wait for something, use timer to periodically check for it

3. Use async method when you have I/O Tasks