问Exchange插件--如何使用C#获取发送电子邮件的发件人的电子邮件地址？

EN

namespace OutlookTesting
{
    public partial class ThisAddIn
    {
        private void ThisAddIn_Startup(object sender, System.EventArgs e)
        {
            this.Application.ItemSend += new Microsoft.Office.Interop.Outlook.ApplicationEvents_11_ItemSendEventHandler(Application_ItemSend);
        }

        void Application_ItemSend(object Item, ref bool Cancel)
        {
            if (Item is Outlook.MailItem)
            {
                Outlook.MailItem mail = (Outlook.MailItem)Item;
                Debug.WriteLine("Using GetSenderSMTPAddress function: " + GetSenderSMTPAddress(mail));
                Debug.WriteLine("Using mail.SenderEmailAddresss: " + mail.SenderEmailAddress);
                Debug.WriteLine("Using mail.Sender.Address: " + mail.Sender.Address);
            }
        }

        private string GetSenderSMTPAddress(Outlook.MailItem mail)
        {
            string PR_SMTP_ADDRESS =
                @"http://schemas.microsoft.com/mapi/proptag/0x39FE001E";
            if (mail == null)
            {
                throw new ArgumentNullException();
            }
            if (mail.SenderEmailType == "EX")
            {
                Outlook.AddressEntry sender = mail.Sender;
                if (sender != null)
                {
                    //Now we have an AddressEntry representing the Sender
                    if (sender.AddressEntryUserType ==
                        Outlook.OlAddressEntryUserType.
                        olExchangeUserAddressEntry
                        || sender.AddressEntryUserType ==
                        Outlook.OlAddressEntryUserType.
                        olExchangeRemoteUserAddressEntry)
                    {
                        //Use the ExchangeUser object PrimarySMTPAddress
                        Outlook.ExchangeUser exchUser =
                            sender.GetExchangeUser();
                        if (exchUser != null)
                        {
                            return exchUser.PrimarySmtpAddress;
                        }
                        else
                        {
                            return null;
                        }
                    }
                    else
                    {
                        return sender.PropertyAccessor.GetProperty(
                            PR_SMTP_ADDRESS) as string;
                    }
                }
                else
                {
                    return null;
                }
            }
            else
            {
                return mail.SenderEmailAddress;
            }
        }
        #region VSTO generated code

        /// <summary>
        /// Required method for Designer support - do not modify
        /// the contents of this method with the code editor.
        /// </summary>
        private void InternalStartup()
        {
            this.Startup += new System.EventHandler(ThisAddIn_Startup);
        }

        #endregion
    }
}