Imagine that you need to handle from the ViewModel the SelectedIndexChanged of a WPF TreeView, currently the only way (without using any particular framework) is to build your own Behavior to achieve that, or bind, via a style the IsSelected property of the node to a property of the view model, but in this second case the side effect is that to find the selected item you need to visit the whole tree.

Enter Radical “Handle”

<TreeView Margin="5"
ItemsSource="{Binding Path=Accounts}">
<behaviors:Handle RoutedEvent="TreeView.SelectedItemChanged"
WithCommand="{Binding Path=SelectOutlookPath}"
PassingIn="$args.NewValue" />
<!-- omitted -->

As you can imagine the value of the NewValue property of the event arguments is passed as the command parameter to the command, we currently support to placeholder:

  • $args: the routed event arguments;
  • $this: the WPF element the behavior is attached to;
  • $source: the source of the routed event;
  • $originalSource: the original source of the routed event;

Obviously the event we need to handle must be a RoutedEvent.

Available in the Nuget package “Radical.Windows