Subscribe PropertyChanged events of window in C++/CLI

Question

I just tried to subscribe to WPF property change events using C++/CLI. I didn't expect this to get difficult.

First I tried to subscribe to a specific property of some window (IsMouseDirectlyOver) and finally succeeded with following code:

void MyClass::DependencyPropertyChanged(Object^ sender, DependencyPropertyChangedEventArgs args)
{
   Debug::WriteLine("DependencyPropertyChanged: "+sender->ToString()+", "+args.Property->Name);
}

window->IsMouseDirectlyOverChanged += gcnew DependencyPropertyChangedEventHandler(this, &MyClass::DependencyPropertyChanged);

Then I tried to subscribe to any property changes of an object (which is most important to me because my final code must be able to handle property changes by property names). I totally failed on this.

I tried various things but nothing worked. I could not find any C++/CLI examples but according to documentation and C# examples the following seemed to be the most sensible code to me:

window->PropertyChanged += gcnew PropertyChangedEventHandler(this, &MyClass::PropertyChanged);

void MyClass::PropertyChanged(Object^ sender, PropertyChangedEventArgs^ args)
{
   ...
}

But the compiler tells me by error C2039 that 'PropertyChangedEvent' is no element of 'System::Windows::Window'.

How can I achieve what I want?

Answer 1

I had a look on the snoop sources. I modified it and wrote a very, very basic example that works:

String^ ownerPropertyName = "IsActive";
DependencyObject^ propertyOwner = window;

DependencyPropertyDescriptor^ ownerPropertyDescriptor = DependencyPropertyDescriptor::FromName(ownerPropertyName, propertyOwner->GetType(), propertyOwner->GetType());
DependencyProperty^ ownerProperty = ownerPropertyDescriptor->DependencyProperty;
Type^ ownerPropertyType = ownerProperty->PropertyType;

DependencyProperty^ myProperty = DependencyProperty::Register(ownerPropertyName, ownerPropertyType, GetType(), gcnew PropertyMetadata(gcnew PropertyChangedCallback(&MyClass::BoundPropertyChangedCallback)));

Binding^ myPropertyToOwnerPropertyBinding = gcnew Binding(ownerPropertyName);
myPropertyToOwnerPropertyBinding->Mode = BindingMode::OneWay;
myPropertyToOwnerPropertyBinding->Source = propertyOwner;
BindingOperations::SetBinding(this, myProperty, myPropertyToOwnerPropertyBinding);

And:

static void BoundPropertyChangedCallback(DependencyObject^ me, DependencyPropertyChangedEventArgs args)
{
   Debug::WriteLine("BoundPropertyChangedCallback: "+args.OldValue+", "+args.NewValue+", "+args.Property->Name);
}

Looks pretty complicated to me. I have no idea if that binding stuff is really necessary. In fact this can even subscribe to properties that do not have events (like IsMouseOver) and can operate on objects that do not implement INotifyPropertyChanged (like Window). And it does not need any switch/case for properties.