Identifying Notifications in an HttpWebResponse

Common to all push notification types is an optional custom header named X-MessageID, which can be added to the HttpWebRequest.Headers collection. Its purpose is to uniquely identify the notification message, and if present, the same value is able to be retrieved in the notification response. It must be a string that contains a universally unique identifier (UUID), as shown in the following excerpt:

request.Headers.Add("X-MessageID", "<UUID>");

At the time of writing, this header does not serve any purpose, because the resulting HttpWebResponse is retrieved using the original HttpWebRequest. It is, therefore, trivial to identify a notification based on an HttpWebResponse. In the future, however, this setting may be used in conjunction with an MPNS callback, to update the cloud service if a notification is impacted because of, for example, session expiry.