Code

 private void Calendar_ItemModified(object sender, ItemModifiedEventArgs e)
        {
	   var item = e.Item;
            var executeUndo = false;

            MindFusion.Scheduling.Item appChangeItem = item;
            MindFusion.Scheduling.Schedule appSchedule = this.calendar.Schedule;
            MindFusion.Scheduling.ChangeItemCommand appChangeCommand = null;

            this.calendar.BeginInit();
            appSchedule.UndoEnabled = true;
            appSchedule.StartCompositeOperation();
            appChangeCommand = new MindFusion.Scheduling.ChangeItemCommand(appSchedule, appChangeItem);

            //I want to undo the change command when db update failed.
            executeUndo = true;

            appSchedule.ExecuteCommand(appChangeCommand);
            appSchedule.CommitCompositeOperation();
            if (executeUndo)
            {
                appSchedule.Undo();
            }
            appSchedule.UndoEnabled = false;
            this.calendar.EndInit();
        }
 

Code

Dispatcher.InvokeAsync(() => calendar.Schedule.Undo());