它只工作一次,而不是事件处理程序不起作用。我不明白为什么?
private void ThisAddIn_Startup(object sender, System.EventArgs e) {
    var folder = Globals.ThisAddIn.Application.Session.DefaultStore.
                   GetDefaultFolder(Outlook.OlDefaultFolders.olFolderTasks);
    foreach(Outlook.TaskItem item in folder.Items) {
        item.BeforeDelete += BeforeDelete;
        item.Save();
    }
}
private void BeforeDelete(object item, ref bool cancel) {
    MessageBox.Show("Удалено");
    // Marshal.ReleaseComObject(item); must I do It?
}