IClosableNotifier Interface
Definition
Important
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When implemented in a WinRT runtime class, provides notification that an object has been closed (disposed).
public interface class IClosableNotifier/// [Windows.Foundation.Metadata.ContractVersion(Microsoft.Foundation.WindowsAppSDKContract, 65540)]
/// [Windows.Foundation.Metadata.Guid(696903995, 60687, 24185, 144, 242, 234, 197, 146, 252, 110, 106)]
struct IClosableNotifier[Windows.Foundation.Metadata.ContractVersion(typeof(Microsoft.Foundation.WindowsAppSDKContract), 65540)]
[Windows.Foundation.Metadata.Guid(696903995, 60687, 24185, 144, 242, 234, 197, 146, 252, 110, 106)]
public interface IClosableNotifierPublic Interface IClosableNotifier- Derived
- Attributes
Remarks
The purpose of this interface is to provide a reliable notification when the underlying object is closed (disposed) and also a way to check if the object is closed.
Typically, an object would need to know when another WinRT object is closed if it depends on that WinRT object to satisfy its functionality. If the WinRT object it depends on is closed, you can perform cleanup operations and/or unregister from events.
Object state when events are raised
When the the Closed or FrameworkClosed event is processed, the underlying WinRT object is already closed. If you attempt to access the object's properties (except IsClosed) or methods, RO_E_CLOSED is returned after this point. The only operations that are allowed are unsubscribing from events and checking the IsClosed property on the object.
Order of events
The Closed and FrameworkClosed events are raised in pairs. First the FrameworkClosed event is raised to give frameworks a chance to clean up their state, then the Closed event is raised to also give application code a chance to clean up.
Frameworks respond to the first event so that they can prepare for an application to call into the framework after the object is closed. For example, a framework may null-out internal state so that applications that try to use that state will receive an appropriate error rather than trying to operate on an invalid state.
Possible ways a WinRT object can be closed
- If the WinRT object is bound to a certain thread, it is typically closed when the thread exits.
- If the WinRT object implements
IClosable.Close, external code can explicitly request that it be closed. - If the last strong reference to the object has been released, the object can be closed.
No sender or args for the event
If the Closed and FrameworkClosed events are raised on a WinRT object that has been disposed and doesn't have any more strong references holding it in memory, then the sender and event args parameters of a TypedEventHandler would be null. In order to support this case, these events do not provide the sender or event args and the ClosableNotifierHandler does not take any parameters. The subscriber to the events is responsible for knowing to which WinRT object it is subscribed to.
Properties
| IsClosed |
Gets a value that indicates whether the object is closed (disposed). |
Events
| Closed |
Occurs when the object has been closed (disposed), after the FrameworkClosed event, to notify the app that the object is closed. |
| FrameworkClosed |
Occurs when the object has been closed (disposed), before the Closed event, to notify the framework (such as XAML) that the object is closed. |