Avalonia threading¶

The ReactiveUI.Binding.Avalonia package adds WithAvalonia and AvaloniaBindingModule. The module registers the invoker from the walkthrough, an observer for registered Avalonia properties, and a command binder that uses a control's Command property or a routed event. None of them reflect over members, so the package is safe to trim and to publish ahead of time. A progress report from a pool thread waits for the UI thread. The example below binds an upload's progress to a progress bar. The upload reports progress from pool threads, and the invoker moves each write to the UI thread.

StorageBrowserViewModel viewModel = new(InMemoryObjectStorage.CreateSeeded());
await viewModel.LoadBucketsAsync();
viewModel.SelectedBucket = viewModel.Buckets[0];
AvaloniaUploadView view = new() { ViewModel = viewModel };
UploadRequest photo = new(OffsitePhotoName, OffsitePhotoSize, JpegType);

using (viewModel.BindOneWay(view, x => x.UploadPercent, v => v.UploadProgressBar.Value))
{
    Console.WriteLine(view.UploadProgressBar.Value);

    await viewModel.UploadAsync(photo);

    Console.WriteLine(view.UploadProgressBar.Value);
}

0
100

An Avalonia control raises PropertyChanged with the name of the property. That is the notification the engine observes, so WhenChanged works on Avalonia controls without more setup. The example below subscribes to the control's own PropertyChanged event and prints the property name it raises. It shows the notification the engine relies on.

AvaloniaTodoView view = new();
INotifyPropertyChanged notifying = (INotifyPropertyChanged)view.FilterTextBox;
notifying.PropertyChanged += static (_, e) => Console.WriteLine(e.PropertyName);

view.FilterTextBox.Text = CarFilter;

Text

WhenChanged observes that event. The example below observes Text and sets the text once. The first value is the empty text the box held when the observation started, and the second is the new text.

AvaloniaTodoView view = new();
List<string?> texts = [];

using (view.FilterTextBox.WhenChanged(x => x.Text).Subscribe(texts.Add))
{
    view.FilterTextBox.Text = CarFilter;
}

Console.WriteLine(string.Join(", ", texts));

, car

API reference¶