How to perform "nslookup host server"

The problem was solved!

http://msdn.microsoft.com/en-us/library/ms682016(VS.85).aspx

See "Great Example here" section

[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);

...

I looked into this a while back. It is not possible in the standard class libraries, so you are going to have to use an external component to do this properly.

There are a number of free and paid choices available to you. My implementation was based around a posting on CodeProject, which worked quite well. DNS Client Library for .NET (also mentioned by kprobst) was released after I finished mine, or I would've used this one initially.