Region content lifecycle

A region, as every other contet in Radical, has a lifecycle. Depending on the type of the region the lifecycle can be different, but the general approach is the following:

• View and ViewModel will be released;

• If View or ViewModel implements IDisposable they will be disposed;

• If View or ViewModel implements IExpectViewClosedCallback they will receive a callback notification;

Every region can be Shutdown, not explicitely, but by shutting down the RegionManager that manages the region. A RegionManager shutdown can occour, for example, at application shutdown or when the hosting Window is closed. At shutdown time every region managed by the shutdown RegionManager will be notified and the region content, in our case the ViewModel, has the opportunity to intercept and react to this process.

When ever is region content is removed the entire logical tree of the removed content is inspected to ensure that is it contains any other regions their lifecycle is managed as expected sutting down all the nested regions.

IContentRegion

An IContentRegion notifies its own content ViewModel, if any, right before removing the content and once it has been removed. The content ViewModel has the opportunity, via the IExpectViewClosingCallback, to cancel the removal process and to be notified once the removal is comleted via the IExpectViewClosedCallback.

IElementsRegion

An IElementsRegion can host multiple contents at a time, it is designed to notify the ViewModel, if any, of the content that will be removed right before removing it and once it has been removed. The content ViewModel has the opportunity, via the IExpectViewClosingCallback, to cancel the removal process and to be notified once the removal is completed via the IExpectViewClosedCallback.

ISwitchingElementsRegion

An ISwitchingElementsRegion can host multiple contents at a time as the IElementsRegion and add the concept of an active content that can change over time. It is designed to notify the ViewModel, if any, of the content that will be removed right before removing it and once it has been removed. The content ViewModel has the opportunity, via the IExpectViewClosingCallback, to cancel the removal process and to be notified once the removal is completed via the IExpectViewClosedCallback. Other than behaving as a IElementsRegion the ISwitchingElementsRegion notifies each content ViewModel whenever is activated if it implements the IExpectViewActivatedCallback.