DependencyProperty::RegisterAttached Method (String, Type, Type, PropertyMetadata)
Registers an attached property with the specified property name, property type, owner type, and property metadata.
Assembly: WindowsBase (in WindowsBase.dll)
public: static DependencyProperty^ RegisterAttached( String^ name, Type^ propertyType, Type^ ownerType, PropertyMetadata^ defaultMetadata )
- Type: System::String
The name of the dependency property to register.
- Type: System::Type
The type of the property.
- Type: System::Type
The owner type that is registering the dependency property.
- Type: System.Windows::PropertyMetadata
Property metadata for the dependency property. This can include the default value as well as other characteristics.
Return ValueType: System.Windows::DependencyProperty
A dependency property identifier that should be used to set the value of a public static readonly field in your class. That identifier is then used to reference the dependency property later, for operations such as setting its value programmatically or obtaining metadata.
An attached property is a property concept defined by Extensible Application Markup Language (XAML). WPF implements attached properties as dependency properties. Because the WPF attached properties are dependency properties, they can have metadata applied that can be used by the general property system for operations such as reporting layout characteristics. For more information, see Attached Properties Overview.
For more information on dependency property registration, see DependencyProperty.
Use RegisterAttached for Value-inheriting Dependency Properties
One particular scenario for registering a dependency property with RegisterAttached instead of Register is to support property value inheritance. You should register value-inheriting dependency properties with RegisterAttached even if the class defines property wrapper accessors that expose the dependency property, and even if you do not intend to expose Get* and Set* static methods to provide true attached property support accessors. Although property value inheritance might appear to work for nonattached dependency properties, the inheritance behavior for a nonattached property through certain element boundaries in the runtime tree is undefined. Registering the property as attached effectively makes the attached property a global property to the property system, and assures that property value inheritance works across all boundaries in an element tree. Always use RegisterAttached to register properties where you specify Inherits in the metadata. For more information, see Property Value Inheritance.
This example shows how to register an attached property and provide public accessors so that you can use the property in both Extensible Application Markup Language (XAML) and code. Attached properties are a syntax concept defined by Extensible Application Markup Language (XAML). Most attached properties for WPF types are also implemented as dependency properties. You can use dependency properties on any DependencyObject types.
The following example shows how to register an attached property as a dependency property, by using the RegisterAttached method. The provider class has the option of providing default metadata for the property that is applicable when the property is used on another class, unless that class overrides the metadata. In this example, the default value of the IsBubbleSource property is set to false.
The provider class for an attached property (even if it is not registered as a dependency property) must provide static get and set accessors that follow the naming convention Set[AttachedPropertyName] and Get[AttachedPropertyName]. These accessors are required so that the acting XAML reader can recognize the property as an attribute in XAML and resolve the appropriate types.