ListBox.SelectedItems的TwoWay手动绑定实现？

I've been trying to see if there is an easy/clever way to implement binding to ListBox.SelectedItems. If you have tried yourself, you will know, that markup binding using BindingExtension will not work - the property doesn't support it. So you are left with wiring up a handler for SelectionChanged and trying that route. The closest I've gotten is this post:I've been trying to see if there is an easy/cle