mscorlib 4.0.0.0 Covariant To be added.

The and interfaces provide a generalized mechanism for push-based notification, also known as the observer design pattern. The interface represents the class that sends notifications (the provider); the interface represents the class that receives them (the observer). represents the class that provides the notification information. In some push-based notifications, the implementation and can represent the same type.

The provider must implement a single method, , that indicates that an observer wants to receive push-based notifications. Callers to the method pass an instance of the observer. The method returns an implementation that enables observers to cancel notifications at any time before the provider has stopped sending them.

At any given time, a given provider may have zero, one, or multiple observers. The provider is responsible for storing references to observers and ensuring that they are valid before it sends notifications. The interface does not make any assumptions about the number of observers or the order in which notifications are sent.

The provider sends the following three kinds of notifications to the observer by calling methods:

The current data. The provider can call the method to pass the observer a object that has current data, changed data, or fresh data.

An error condition. The provider can call the method to notify the observer that some error condition has occurred.

No further data. The provider can call the method to notify the observer that it has finished sending notifications.

Defines a provider for push-based notification.

- Method
  4.0.0.0
  System.IDisposable `` To be added. To be added. To be added. To be added.