private void buttonCloseExplorer_Click(object sender, EventArgs e)
        {
            try
            {
                Outlook.MailItem
                    mailItem = null;

                Outlook.Explorer
                    explorer = null;

                try
                {
                    if ((mailItem = OutlookItem as Outlook.MailItem) != null &&
                        (explorer = mailItem.Application.ActiveExplorer()) != null)
                    {
                        explorer.Close();
                    }
                }
                finally
                {
                    if (explorer != null)
                    {
                        Marshal.ReleaseComObject(explorer);
                        explorer = null;
                    }

                    if (mailItem != null)
                    {
                        Marshal.ReleaseComObject(mailItem);
                        mailItem = null;
                    }
                }
            }
            catch (Exception eException)
            {
                string msg;

                ThisAddIn.WriteToLog(msg = eException.GetType().FullName + Environment.NewLine + "Message: " + eException.Message + Environment.NewLine + (eException.InnerException != null && !string.IsNullOrEmpty(eException.InnerException.Message) ? "InnerException.Message" + eException.InnerException.Message + Environment.NewLine : string.Empty) + "StackTrace:" + Environment.NewLine + eException.StackTrace);
                textBoxLog.Text          = msg;
            }
        }
 public override void Close()
 {
     explorer.Close();
 }