CODEWITHSUNDEEP
c#dns
Bill Greer
Bill Greer

Reputation: 3156

How to properly check if a DNS entry exists using c#

I have a list of computers by name. I'd like to see if the computers on the network are connected by using the System.Net.Ping and System.Net.PingReply. The list of computers may become stale from time to time. If the host is not found I get an exception. Is there a way that I can check to see if there is a record of the host without experiencing an exception? I thought I might be able to use Dns.GetHostEntry(c.Name) but this also returns an exception if the host is not in DNS.

Upvotes: 1

Views: 1533

Answers (1)

Kitson88
Kitson88

Reputation: 2940

If you're unable to use a try/catch, you could use SimpleDNS (Nuget as well) which only throws exceptions on connection issues to the chosen DNS server.

var dnsServer = IPAddress.Parse("8.8.8.8");
var result = Query.Simple(new SimpleDnsPacket(new Question("lalalalalaldasl.com", QType.A), dnsServer)); //Failing Query

The return DNS packet object will be null if query was invalid:

enter image description here

and rather than checking for null, you could query the Response property found in the Header:

//Continued on from above....

if (result.Header.Parameters.Response != ResponseCode.Ok)
{
      //Something here!
}

Upvotes: 2

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