WPF – nested windows

Question

My application consists of 2 main components. Each of them has specific functionality. Each of them is half-width of parent and always visible.

I use BackgroundWorker for working with data, but problem is that also UI refresh is sometimes long operation. And the main problem is: one component freezes = application freeze.

So I looking for solution how to run each component on specific Thread.

I think that best is run each component in specific Window (= UI thread for each Window). If one component freezes other can run.

I also read article about VisualHost, but with this solution you are unable to interact with the control.

But actually I can't find solution, how to nested this component's Windows inside Main Window. Any help, please?

you are still doing things in Win form way. With WPF you should have a view model which should start its own thread if its doing cpu intense work to avoid blocking UI thread. Use async/await instead of Backgroundworker if you are on .net 4.5+ — Steve
– Steve, Commented Aug 31, 2016 at 15:09
Thank you, Steve, for quick reply. I use MVVM pattern. I think that problem is in refreshing of UI – that must be executed on main UI thread and sometimes freeze all application. — David
– David, Commented Aug 31, 2016 at 15:17
I think that is similar to my problem: stackoverflow.com/questions/10029109/…. But I don't understand the solution. — David
– David, Commented Aug 31, 2016 at 15:29

Sarel Louw · Accepted Answer · 2016-08-31 15:34:05Z

3

In the following article MVVM : Multithreading and Dispatching in MVVM Applications you will see how the Microsoft .NET Framework handles threads and what precautions need to be taken when a background thread wants to modify an object created by the main thread (also called the UI thread). You will see how this can cause a crash, and to avoid this crash, the main thread’s Dispatcher should be used to properly handle the operation. Hope this can help you. https://msdn.microsoft.com/en-us/magazine/dn630646.aspx

answered Aug 31, 2016 at 15:34

Sarel Louw

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2 Comments

David Over a year ago

Thank you, Sarel, for tip. Actually I don't have problem with "permission" to update UI components. Problem is that it is sometimes slow operation.

Sarel Louw Over a year ago

like Steve mentioned Async/Await is also an option.

StepUp · Accepted Answer · 2016-08-31 16:31:52Z

Without code is hard to help. However, the main idea is to execute long-intensive operations on the non-UI thread to avoid freezing your UI.

For example(without MVVM pattern):

 private void Button_Click(object sender, RoutedEventArgs e)
    {
        Task.Run(() =>
        {
            Thread.Sleep(3000);
            txtBox.Dispatcher.Invoke(DispatcherPriority.Normal,
                  new Action(() => { txtBox.Text = "I am a TextBox"; }));
        });
    }

With MVVM pattern:

XAML:

<TextBlock Text="{Binding Number}" FontSize="188" Foreground="Red" />
ViewModel:

ViewModel:

public int Number { get; set; }

private void UpdateNumber()
{
        Task.Run(() => 
        {
            System.Timers.Timer timer = new System.Timers.Timer(250);
            timer.Elapsed += (sender, eventArgs) =>
            { 
                Number++;
                OnPropertyChanged("Number");//No exceptions, no errors
            };
            timer.Enabled = true;
        });
}

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