C# Signature:
[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);
VB Signature:
Private Declare Unicode Function DnsQuery Lib "dnsapi" Alias "DnsQuery_W" (<MarshalAs(UnmanagedType.VBByRefStr)> _
ByRef pszName As String, ByVal wType As QueryTypes, ByVal options As QueryOptions, ByVal aipServers As Integer, ByRef ppQueryResults As IntPtr, ByVal pReserved As Integer) As Integer
User-Defined Types:
C#
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_QUERY_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_A = 1
DNS_TYPE_NS = 2
DNS_TYPE_CNAME = 5
DNS_TYPE_SOA = 6
DNS_TYPE_PTR = 12
DNS_TYPE_HINFO = 13
DNS_TYPE_MX = 15
DNS_TYPE_TXT = 16
DNS_TYPE_AAAA = 28
}
[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;
}
Alternative Managed API:
Do you know one? Please contribute it!
Notes:
Example provided by Peter A Bromberg, Ph.D.
http://www.eggheadcafe.com/articles/20050129.asp
* additional QueryTypes added by AzerothNil
Tips & Tricks:
Please add some!
Sample Code:
C#
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(ptr1, 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_QUERY_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_A = 1
DNS_TYPE_NS = 2
DNS_TYPE_CNAME = 5
DNS_TYPE_SOA = 6
DNS_TYPE_PTR = 12
DNS_TYPE_HINFO = 13
DNS_TYPE_MX = 15
DNS_TYPE_TXT = 16
DNS_TYPE_AAAA = 28
}
[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;
}
}
VB
Imports System
Imports System.Collections
Imports System.ComponentModel
Imports System.Runtime.InteropServices
Public Class DnsMx
Public Sub New()
End Sub
Private Declare Unicode Function DnsQuery Lib "dnsapi" Alias "DnsQuery_W" (<MarshalAs(UnmanagedType.VBByRefStr)> _
ByRef pszName As String, ByVal wType As QueryTypes, ByVal options As QueryOptions, ByVal aipServers As Integer, ByRef ppQueryResults As IntPtr, ByVal pReserved As Integer) As Integer
<DllImport("dnsapi", CharSet := CharSet.Auto, SetLastError := True)> _
Private Shared Sub DnsRecordListFree(ByVal pRecordList As IntPtr, ByVal FreeType As Integer)
End Sub
Public Shared Function GetMXRecords(ByVal domain As String) As String()
Dim ptr1 As IntPtr = IntPtr.Zero
Dim ptr2 As IntPtr = IntPtr.Zero
Dim recMx As MXRecord
If Environment.OSVersion.Platform <> PlatformID.Win32NT Then
Throw New NotSupportedException()
End If
Dim list1 As New ArrayList()
Dim num1 As Integer = DnsMx.DnsQuery(domain, QueryTypes.DNS_TYPE_MX, QueryOptions.DNS_QUERY_BYPASS_CACHE, 0, ptr1, 0)
If num1 <> 0 Then
Throw New Win32Exception(num1)
End If
ptr2 = ptr1
While Not ptr2.Equals(IntPtr.Zero)
recMx = DirectCast(Marshal.PtrToStructure(ptr2, GetType(MXRecord)), MXRecord)
If recMx.wType = 15 Then
Dim text1 As String = Marshal.PtrToStringAuto(recMx.pNameExchange)
list1.Add(text1)
End If
ptr2 = recMx.pNext
End While
DnsMx.DnsRecordListFree(ptr1, 0)
Return DirectCast(list1.ToArray(GetType(String)), String())
End Function
Private Enum QueryOptions
DNS_QUERY_ACCEPT_TRUNCATED_RESPONSE = 1
DNS_QUERY_BYPASS_CACHE = 8
DNS_QUERY_DONT_RESET_TTL_VALUES = 1048576
DNS_QUERY_NO_HOSTS_FILE = 64
DNS_QUERY_NO_LOCAL_NAME = 32
DNS_QUERY_NO_NETBT = 128
DNS_QUERY_NO_RECURSION = 4
DNS_QUERY_NO_WIRE_QUERY = 16
DNS_QUERY_RESERVED = -16777216
DNS_QUERY_RETURN_MESSAGE = 512
DNS_QUERY_STANDARD = 0
DNS_QUERY_TREAT_AS_FQDN = 4096
DNS_QUERY_USE_TCP_ONLY = 2
DNS_QUERY_WIRE_ONLY = 256
End Enum
Private Enum QueryTypes
DNS_TYPE_A = 1
DNS_TYPE_NS = 2
DNS_TYPE_CNAME = 5
DNS_TYPE_SOA = 6
DNS_TYPE_PTR = 12
DNS_TYPE_HINFO = 13
DNS_TYPE_MX = 15
DNS_TYPE_TXT = 16
DNS_TYPE_AAAA = 28
End Enum
<StructLayout(LayoutKind.Sequential)> _
Private Structure MXRecord
Public pNext As IntPtr
Public pName As String
Public wType As Short
Public wDataLength As Short
Public flags As Integer
Public dwTtl As Integer
Public dwReserved As Integer
Public pNameExchange As IntPtr
Public wPreference As Short
Public Pad As Short
End Structure
End Class
