How to get Email Address From AD

Hello,
i have an aspx page which on page load needs to populate a text box with the current users email address (user is in Active Directory), any body know how to retrieve the email address from Active Directory, i have read this article on the web but am a bit confused
string userName = Environment.UserName;
string domainName = Environment.UserDomainName;

//Set the correct format for the AD query and filter
string ldapQueryFormat = @"LDAP://{0}.com/DC={0},DC=com";
string queryFilterFormat = @"(&(samAccountName={0})(objectCategory=person)(objectClass=user))";

SearchResult result = null;
using(DirectoryEntry root = newDirectoryEntry(rootQuery))
{
    using(DirectorySearcher searcher = new DirectorySearcher(root))
    {
        searcher.Filter = searchFilter;
        SearchResultC ...