Code

private void Create_Click(object sender, RoutedEventArgs e)
        {
            var item = new Appointment();
            item.Subject = "aaa";
            item.StartTime = new DateTime(2023, 10, 2);
            item.EndTime = new DateTime(2023, 10, 3);
            calendar.Schedule.Items.Add(item);
            appointment_id = item.Id;
            item.Recurrence = new Recurrence()
            {
                Pattern = RecurrencePattern.Weekly,
                DaysOfWeek = DaysOfWeek.Monday,
                StartDate = item.StartTime,
                DailyRecurrence = DailyRecurrence.ByDayInterval,
                NumOccurrences = 3,
                RecurrenceEnd = RecurrenceEnd.NumOccurrences,
            };
			item.Reminder = new Reminder()
			{
				Type = ReminderType.Leading,
				TimeInterval = TimeSpan.FromMinutes(15)
			};


            // Edit the clicked item
            var edititem = item.Recurrence.GetOccurrence(1);
            var editWindow = new EditWindow(calendar.Schedule);
            editWindow.SetAppointment(edititem);
            editWindow.Activate();
            editWindow.Show();
        }
 

Code

public partial class EditWindow : Window
    {
        MindFusion.Scheduling.Schedule schedule { get; set; }
        MindFusion.Scheduling.Item item { get; set; }

        public EditWindow(MindFusion.Scheduling.Schedule schedule)
        {
            InitializeComponent();

            this.schedule = schedule;
        }

        public void SetAppointment(Item item)
        {
            this.item = item;
        }

        private void Remove_Click(object sender, RoutedEventArgs e)
        {
            this.schedule.Items.Remove(this.item);

            //Dispatcher.InvokeAsync(() =>
            //{
            //
            //});
            this.Close();
        }