/*
* public static bool operator<(MXRecord record1, MXRecord record2)
* {
* if (record1._preference > record2._preference) return false;
* if (record1._domainName > record2._domainName) return false;
* return false;
* }
*
* public static bool operator>(MXRecord record1, MXRecord record2)
* {
* if (record1._preference < record2._preference) return false;
* if (record1._domainName < record2._domainName) return false;
* return false;
* }
*/
public override bool Equals(object obj)
{
// this object isn't null
if (obj == null)
{
return(false);
}
// must be of same type
if (this.GetType() != obj.GetType())
{
return(false);
}
MXRecord mxOther = (MXRecord)obj;
// preference must match
if (mxOther._preference != _preference)
{
return(false);
}
// and so must the domain name
if (mxOther._domainName != _domainName)
{
return(false);
}
// its a match
return(true);
}
/// <summary>
/// Shorthand form to make MX querying easier, essentially wraps up the retreival
/// of the MX records, and sorts them by preference
/// </summary>
/// <param name="domain">domain name to retreive MX RRs for</param>
/// <param name="dnsServer">the server we're going to ask</param>
/// <returns>An array of MXRecords</returns>
public static MXRecord[] MXLookup(string domain, IPAddress dnsServer)
{
// check the inputs
if (domain == null)
{
throw new ArgumentNullException("domain");
}
if (dnsServer == null)
{
throw new ArgumentNullException("dnsServer");
}
// create a request for this
Request request = new Request();
// add one question - the MX IN lookup for the supplied domain
request.AddQuestion(new Question(domain, DnsType.MX, DnsClass.IN));
// fire it off
Response response = Lookup(request, dnsServer);
// if we didn't get a response, then return null
if (response == null)
{
return(null);
}
// create a growable array of MX records
ArrayList resourceRecords = new ArrayList();
// add each of the answers to the array
foreach (Answer answer in response.Answers)
{
// if the answer is an MX record
if (answer.Record.GetType() == typeof(MXRecord))
{
// add it to our array
resourceRecords.Add(answer.Record);
}
}
// create array of MX records
MXRecord[] mxRecords = new MXRecord[resourceRecords.Count];
// copy from the array list
resourceRecords.CopyTo(mxRecords);
// sort into lowest preference order
Array.Sort(mxRecords);
// and return
return(mxRecords);
}
/// <summary>
/// Implements the IComparable interface so that we can sort the MX records by their
/// lowest preference
/// </summary>
/// <param name="other">the other MxRecord to compare against</param>
/// <returns>1, 0, -1</returns>
public int CompareTo(object obj)
{
MXRecord mxOther = (MXRecord)obj;
// we want to be able to sort them by preference
if (mxOther._preference < _preference)
{
return(1);
}
if (mxOther._preference > _preference)
{
return(-1);
}
// order mail servers of same preference by name
return(-mxOther._domainName.CompareTo(_domainName));
}