WPF PropertyMetadata Change Event to inject code

PropertyMetadata has the following signature
new PropertyMetadata (false,OnChanged)

        private void OnChanged(DependencyObject d, DependencyPropertyChangedEventArgs e){}
It can be uses to inject code

(1) ViewModelLocator  --- Wire up View DataContext to a ViewModel.

  //just as normal Dependency property declaration
public static readonly DependencyProperty AutoWireViewModelProperty = 
     DependencyProperty.Register( "AutoWireViewModel", typeof(bool),
     typeof(VMLocators), new PropertyMetadata(false,OnChanged));

  // then create ViewModel as DataContext
  void OnChanged(DependencyObj d,PropChangedEventArgs e) {
    var vmType=d.GetType().FullName+"Model" //convention
    (FrameworkElement)d.DataContext = Activator.GetInstance(vmType);
}
usage in xmal
<UserControl ... local:VMLocators.AutoWireViewModel="true" >

(2) Similarly as in (1) Loaded Event can trigger method calls through attached property
Similarly for Attached Property Behavior
<UserControl loc:LoadedMethodName="GetDataAsync" />

  var f=d as FrameworkElement; 
   f.Loaded+=() =>{ 
        MethodInfo   mi=d.GetType.GetMethod(e.NewValue);
        mi.Invoke(vm,null);
   }
  ViewModel has async void GetDataAsync() { .. var data= await GetDataAsync(); ...}

(3) WPF regular behavior also has PropertyMeta ChangedEvent and can pop Notification

ShowNotificationMsgBehevior : Behavior
    declare dependency property Message as string
 void OnMsg(d,e) { 
var b=d as ShowNotificationMsgBehevior ; 
b.AssocObj.Content=e.NewValue}
 
<ContentControl>
   <interaction.ShowNotificationMsgBehevior Message={Binding NotifMsg} />