Thanks for your Demo,
But I still get this error with your demo.
Please help me to correct it, Now I'm using ASPxScheduler version 10.1.7.0
Does the workaround method (using the ASPxDataView) from the How to add information to the repeater in the custom appointment form without sending a full postback thread help you?
Hello Oanh and all who are tracking this issue,
We have researched this problem with our developers, and came to the conclusion that this is a problem of the ASP.NET AJAX Extensions (ScriptManager, UpdatePanel) when using them in the Web User Control (ascx). For instance, review the How to register UpdatePanel inside UserControl with ScriptManager on Master page? thread. So, we are unable to fix this problem from our side. As an immediate workaround method, we can only suggest that you create the UpdatePanel dynamically. It seem to work correctly in this situation. Please review the Updatepanel within ASPxRoundPanel and Cannot unregister UpdatePanel with ID 'UpdatePanel1' since it was not registered with the ScriptManager. threads for additional information.