There are many server events allowing to program a calendar: drag&drop, double click cell or appointment, change date, etc. Example also demonstrates how to use CallbackScript event to emit client Java Script code ran on web browser in order to callback request. Use callback to the server DataRetrieving

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If you would look into a source code for this demo, click on the link.
For demonstration purposes all appointments displayed on a calendar are stored in ASP.NET session objects, so original values are restored immediately after a new session object is created.
A list of appointments and resources is intialized every time a new session is started.