/*
* 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>
/// 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));
}
/// <summary>
/// Construct a resource record from a pointer to a byte array
/// </summary>
/// <param name="pointer">the position in the byte array of the record</param>
internal ResourceRecord(Pointer pointer)
{
// extract the domain, question type, question class and Ttl
Domain = pointer.ReadDomain();
Type = (DnsType)pointer.ReadShort();
Class = (DnsClass)pointer.ReadShort();
Ttl = pointer.ReadInt();
// the next short is the record length, we only use it for unrecognized record types
int recordLength = pointer.ReadShort();
// and create the appropriate RDATA record based on the dnsType
switch (Type)
{
case DnsType.NS:
Record = new NSRecord(pointer);
break;
case DnsType.MX:
Record = new MXRecord(pointer);
break;
case DnsType.ANAME:
Record = new ANameRecord(pointer);
break;
case DnsType.CNAME:
Record = new CNameRecord(pointer);
break;
case DnsType.SOA:
Record = new SoaRecord(pointer);
break;
case DnsType.TXT:
Record = new TXTRecord(pointer, recordLength);
break;
default:
{
// move the pointer over this unrecognized record
pointer.Seek(recordLength);
break;
}
}
}