updating webservice with objects when app exits

Im working on a silverlight application where a user can create, edit, delete objects. The changes they make are placed in a queue which is processed every 4 minutes. When it is processed, the updates are sent over an async web method call to be saved in a sql database, one at a time. When the first update finishes, the next starts.

Im having a problem when a user makes a change and then exits the browser app before the 4 minute timer has expired. Currently the changes are getting lost.

Ive built on what the guy working on this before me has done, and explored the Dispose and Finalize methods, tryi开发者_运维百科ng to start the update process when the factory is being shut down, but that isnt working due to the async nature of the web service calls. I get errors saying needed objects have already been disposed of.

Im looking for a way to save the data in the updatequeue using a webmethod when the user tries to close or refresh the webpage. Im not expecting the queue to be packed full with updates. This is an application that would usually be run for several hours at a time.

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You can use Javascript to stop the user leaving the page. StackOverflow does it (try editing an answer and leaving the page). That works on browser close as well as page navigation. From Javascript you can also notify the Silverlight app to save any queued data (Silverlight support exposing methods to Javascript).

Q. Saving every 4 minutes is slightly odd behaviour for a Silverlight App. I am guessing it is only deigned to be run by one user at a time. What restricts you from saving more frequently?