Outlook VSTO addin: Iterating through Exceptions of a recurring meeting during deletion (Item_Add to trashfolder) throws COMException

Question

My Outlook Addin adds info to each AppointmentItem which should get deleted in case the AppointmentItem gets deleted (user hits delete on AppointmentItem in the Calendar).

For this I use the following event handling. On startup I attach to the trash folder:

[...]

Outlook.MAPIFolder trashFolder =
                currentExplorer.Session.GetDefaultFolder(Outlook.OlDefaultFolders.olFolderDeletedItems);
            _DeletedItems = trashFolder.Items;
            _DeletedItems.ItemAdd += Item_Delete_Add;

[...]

Item_Delete_Add gets called when the user hits delete on an appointment series and the user selects "whole series":

[...]

    if (myAppointment.RecurrenceState == Outlook.OlRecurrenceState.olApptMaster)
    {
        DialogResult dialogResult = MessageBox.Show(Resources.Resources.DeleteAllAgreeDoMeetingsInSeries, Resources.Resources.AlsoDeleteAgreeDoMeeting_DialogTitle, MessageBoxButtons.YesNo, MessageBoxIcon.Warning);
        if (dialogResult == DialogResult.Yes)
        {                    
            Outlook.RecurrencePattern pattern = myAppointment.GetRecurrencePattern();
            foreach (Outlook.Exception exception in pattern.Exceptions)
            {
                if (!deleteAppointment(exception.AppointmentItem,true))
                {
                    wasSuccessfull = false;
                }
            }
        }
    } else

[...]

When accessing exception.AppointmentItem the following COMException is thrown:

The german exception description translates to something: You have changed an element of this series. and this instance is not available anymore. Close all elements and try again.

So the question boils down to: How can I handle the deletion of an appointment series in a way so I can handle each exception within the series individually (i.e. delete data stored in that exceptions).

HHeckner HHeckner · Accepted Answer · 2020-05-24T06:03:01

Found the solution here

You just need to check whether the exception has already been deleted by modifying the above code:

[...]

    if (myAppointment.RecurrenceState == Outlook.OlRecurrenceState.olApptMaster)
    {
        DialogResult dialogResult = MessageBox.Show(Resources.Resources.DeleteAllAgreeDoMeetingsInSeries, Resources.Resources.AlsoDeleteAgreeDoMeeting_DialogTitle, MessageBoxButtons.YesNo, MessageBoxIcon.Warning);
        if (dialogResult == DialogResult.Yes)
        {                    
            Outlook.RecurrencePattern pattern = myAppointment.GetRecurrencePattern();
            foreach (Outlook.Exception exception in pattern.Exceptions)
            {
                if (!exception.Deleted)
                {
                    if (!deleteAppointment(exception.AppointmentItem, true))
                    {
                        wasSuccessfull = false;
                    }
                }
            }
        }
    } else

[...]

At least this avoids COMExceptions.

Outlook VSTO addin: Iterating through Exceptions of a recurring meeting during deletion (Item_Add to trashfolder) throws COMException

1 Answers