Based on my observation on the attached code, it seems there is some mistake in the WebScheduler markup.

In the EventsBinding property, you will need to use different column for StartTime and EndTime and you will also need to bind the AllDayEvent field.

<EventsBinding 
  AllDayEventField="..."
  CategoryIDField="IDCategories" 
  DescriptionField="descrizione"
  EndTimeField="oraFine" 
  EventIDField="ID" 
  LocationField="luogo" 
  ModeField="modalita"
  ResourceIDField="IDRisorsa" 
  StartTimeField="oraFine" 
  SubjectField="soggetto"
  ReminderTimeSpanField="promemoria"  />

Also in the ISDataSource Events insert parameter, there is some unaccounted parameter. The parameter that is used for the ISDataSource insert parameter and must be the same with the field binded in the EventsBinding property, except for the ID.

<asp:Parameter Name="IDCategories" Type="String" />
<asp:Parameter Name="IDRisorsa" Type="Int32" />
<asp:Parameter Name="modalita" Type="Int32" />
<asp:Parameter Name="soggetto" Type="String" />
<asp:Parameter Name="descrizione" Type="String" />
<asp:Parameter Name="luogo" Type="String" />
<asp:Parameter Name="allDay" Type="Int32" />
<asp:Parameter Name="oraInizio" Type="String" />
<asp:Parameter Name="oraFine" Type="String" />
<asp:Parameter Name="promemoria" Type="Int32" />

Glenn,

thank you very much!! It was a tricky problem, I spent a full day to solve it with no results and finally it's a copy-paste mistake...I'm very grateful to you, thanks for your reply.