DependencyProperty::AddOwner Method (Type)
Adds another type as an owner of a dependency property that has already been registered.
Assembly: WindowsBase (in WindowsBase.dll)
- Type: System::Type
The type to add as an owner of this dependency property.
This method enables the property system to recognize a dependency property on a type that did not register that particular dependency property initially.
Typically, AddOwner is used to add dependency properties to classes that do not already expose that dependency property through managed class inheritance (class inheritance would cause the wrapper properties to be inherited by the derived class, and thus would provide general members-table access to the dependency property already). AddOwner enables the property system to recognize a dependency property on a type that did not register that dependency property initially.
This signature does not allow for specifying metadata. When you use this method, the metadata is automatically generated for the new DependencyProperty and its owner type. The auto-generated metadata is the result of the merged metadata from all of the base types that have this property defined. If no merged metadata is available, then the default metadata for the property is used. If the property is registered by using the RegisterAttached method, then the default metadata is the same as the metadata that is created when RegisterAttached was called. Otherwise, the PropertyMetadata object is created with the DefaultValue property set to the property type's default and all other properties of the PropertyMetadata is set to nullptr. Use the AddOwner(Type, PropertyMetadata) signature if you want to provide metadata for the version of the dependency property as added to the provided type.
The return value of this method is typically used to declare and expose the dependency property by storing a dependency property identifier. The identifier provides access to the dependency property if you want to call property system APIs against the dependency property, particularly as it exists on the adding owner class. The same property name for both original owner and added owner should be used to indicate the similar functionality. You should use the DependencyProperty return value of the AddOwner method to define the dependency property identifier, and also to declare CLR property wrappers, for dependency properties that are added to types using AddOwner.
The AddOwner methodology recommended above is used when creating the dependency properties that are declared within WPF. For instance, both Border and Control define a BorderBrush dependency property, which have similar functionality. Control defines its BorderBrush property to the property system by calling AddOwner based on the original owner Border and its registered BorderBrushProperty dependency property identifer. The AddOwner return value is then used to establish a new static DependencyProperty field (BorderBrushProperty) for that property on the added owner, and a BorderBrush property wrapper is also declared.