Base class for Context-based decoration, specifically where the instance being decorated (InstanceT ) and the (DecorationT ) are not a class type.

Note that this class won't remove decoration relationships automatically and it needs to be manually removed by the client.

Others

InstanceT

The type of the instance being decorated

DecorationT

The type of the decoration being added to instances

As with ClassToClassDecorator<InstanceT, DecorationT> and other descendants of DecoratorBase<InstanceT, DecorationT>, a goal of ValueToValueDecorator is to be non-invasive and avoid altering behavior based on decoration. However, because neither InstanceT nor DecorationT are a class type, its lifecycle cannot be used to determine when to automatically remove its entry in the decorator; thus, even if the value decorated is no longer in use, decoration based on the instance lifecycle would continue to "pin the decoration into existence" indefinitely, until the client actively calls RemoveDecoration.

Protected Functions

ValueToValueDecorator ( )

Member Functions

void AddDecoration

( InstanceT instance,

DecorationT decoration )

Associates an instance with a decoration.

If this instance was already decorated, the old decoration is removed. If there were any outstanding asynchronous requests for the decoration of this instance (from prior calls to GetDecorationAsync(InstanceT), those requests will be fulfilled as part of this operation.

Parameters

instance

The instance to be decorated

decoration

The decoration to be added to this instance

void RemoveDecoration

( InstanceT instance )

Removes the association between an instance and a decoration.

If this instance had no decoration, this does nothing. If a decoration was removed, note that GetDecorationAsync(InstanceT) will resume returning uncompleted tasks for this instance, which will be completed if and when the instance is decorated again.

Parameters

instance

The instance from which decoration should be removed

bool TryGetDecoration

( InstanceT instance,

out DecorationT decoration )

Synchronously retrieves the decoration associated with an instance, if one is available.

Parameters

instance

The instance for which to retrieve the decoration

decoration

Out parameter to be populated with the decoration if one exists, otherwise null

Returns

True if decoration was populated with a valid decoration, otherwise false

Task< DecorationT > GetDecorationAsync

( InstanceT instance )

Asynchronously retrieves the decoration associated with an instance.

If the instance already has a decoration, the returned task is immediately completed with the currently-available decoration. If no decoration is yet available for this instance, the returned task will only be completed during the call to AddDecoration(InstanceT, DecorationT) for the instance in question.

Parameters

instance

The instance for which to retrieve the decoration

Returns

A task resulting in the decoration associated with instance

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