infopath 2010 person and group retrive email

i want to make the code send email that is picked from active directory inside a text box

 XPathNavigator dataSource;
 dataSource = this.MainDataSource.CreateNavigator();
 string toAddress = dataSource.SelectSingleNode
("/my:myFields/my:toAddress/pc:Person/pc:AccountId",NamespaceManager).Value;
dataSource.SelectSingleNode("//my:field1",NamespaceManager).SetValue(this.User.UserName);

so how can i retrieve person and group email and put it inside a text box and which one of this i should use (account id or account type, display name ).