The ASP.NET WebForms version uses API v1 and it can't be changed.
The selected api affects how the client-side events are processed.
For api=1 only one event is fired for every action, depending on the "*Handling" property. Example
1. EventMoveHadling="CallBack"
When the user finishes drag and drop moving the Scheduler will fire EventMove event on the server side (using a CallBack).
2. EventMoveHandling="JavaScript".
When the user finishes drag and drop moving the Scheduler will fire EventMoveJavaScript event on the client side. If you want to fire the server-side event you need to call it manually form the event handler - dp.eventMoveCallBack().
When using api=2 (not supported in the ASP.NET WebForms version at the moment) the event handling process includes three phases:
1. onEventMove is fired
2. The default action specified using eventMoveHandling is fired
3. onEventMoved is fired
api=2 also uses different structure of event handler parameters (it is always one parameter - "args" - that holds all the properties).
Eventually, the ASP.NET WebForms version will also be switched to api=2.