Binding to Tasks and Observables

You can subscribe to the result of a task or an observable by using the ^ stream binding operator.

Example 1: Binding to an observable

For example if DataContext.Name is an IObservable<string> then the following example will bind to the length of each string produced by the observable as each value is produced

<TextBlock Text="{Binding Name^.Length}"/>

Example 2: Binding to a task

If you need to do some heavy work to load the content of a property you can bind to the result of an async Task<TResult>

Consider you have the following view model which generates some text in a long running process:

public Task<string> MyAsyncText => GetTextAsync();

private async Task<string> GetTextAsync()
{
  await Task.Delay(1000); // The delay is just for demonstration purpose
  return "Hello from async operation";
}

You can bind to the result in the following way:

<TextBlock Text="{Binding MyAsyncText^, FallbackValue='Wait a second'}" />

info

Note: You can use FallbackValue to display some loading indicator.