C # code to query the MX address of DNS

//c# code to query the MX address of DNS
namespace PAB. Dnsutils
{
 using System;
 using System.Collections;
 using System.ComponentModel;
 using System.Runtime.InteropServices;
 
 public class dnsmx
 {
  public dnsmx ()
  {
 }
 
  [DllImport ("Dnsapi", entrypoint= "Dnsquery_w", CharSet=CharSet.Unicode, Setlasterror=true, exactspelling=true )]
  private static extern int DnsQuery ([MarshalAs (UNMANAGEDTYPE.VBBYREFSTR)]ref string pszname, Querytypes Wtype, queryoptions options, int aipservers, ref IntPtr ppQueryResults, int preserved);
 
  [DllImport ("Dnsapi", CharSet=CharSet.Auto, Setlasterror=true)]
  private static extern void Dnsrecordlistfree (IntPtr precordlist, int FreeType);
 
  public static string[] Getmxrecords (string domain)
  {
   IntPtr ptr1=intptr . Zero;
   IntPtr Ptr2=intptr.zero;

Mxrecord RECMX;

if (Environment.OSVersion.Platform!= platformid.win32nt)
{
throw new NotSupportedException ();
}

ArrayList List1 = new ArrayList ();

int num1 = Dnsmx.dnsquery (ref domain, QUERYTYPES.DNS_TYPE_MX, queryoptions.dns_query_bypass_cache, 0, ref ptr1, 0);

if (num1!= 0) {throw new win32exception (NUM1);}

for (ptr2 = PTR1;!ptr2. Equals (IntPtr.Zero); PTR2 = Recmx.pnext)
{
RECMX = (Mxrecord) marshal.ptrtostructure (Ptr2, typeof (Mxrecord));

if (Recmx.wtype = 15)
{
String Text1 = Marshal.ptrtostringauto (Recmx.pnameexchange);
List1. ADD (Text1);
}
}

Dnsmx.dnsrecordlistfree (PTR2, 0);

Return (string[]) List1. ToArray (typeof (String));
}

Private enum Queryoptions {dns_query_accept_truncated_response = 1, Dns_query_bypass_cache = 8, dns_query_dont_reset_ Ttl_values = 0x100000, Dns_query_no_hosts_file = 0x40, Dns_query_no_local_name = 0x20, DNS_QUERY_NO_NETBT = 0x80, Dns_quer Y_no_recursion = 4, Dns_query_no_wire_query = 0x10, dns_query_reserved = -16777216, Dns_query_return_message = 0x200, DNS_ Query_standard = 0, Dns_query_treat_as_fqdn = 0x1000, dns_query_use_tcp_only = 2, dns_query_wire_only = 0x100}

Private enum Querytypes {dns_type_mx = 15}

[StructLayout (LayoutKind.Sequential)]
private struct Mxrecord
{
Public IntPtr Pnext;
public string pname;
public short wtype;
public short wdatalength;
public int flags;
public int dwttl;
public int dwreserved;
Public IntPtr Pnameexchange;
public short wpreference;
public short Pad;
}
}
}

static void Main (string[] args)
{
String[] s= PAB. DnsUtils.DnsMx.GetMXRecords ("microsoft.com");

foreach (String st in S) Console.WriteLine ("Server: {0}", ST);

Console.ReadLine ();
}