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”
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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.