Read DNS entries with .NET

.NET does not have a built-in mechanism for querying DNS records; nevertheless, this is a use case that is required relatively often.

With the help of the NuGet package DnsClient (Apache License), however, handling the query is very simple:

using DnsClient;
using DnsClient.Protocol;

string domain = "schwabencode.com";

LookupClient lookup = new();

// Helper to perform and display a query
async Task QueryAndPrint(QueryType type)
{
    Console.WriteLine($"\n=== {type} Records ===");
    IDnsQueryResponse result = await lookup.QueryAsync(domain, type);

    foreach (DnsResourceRecord? dnsRecord in result.AllRecords)
    {
        switch (dnsRecord)
        {
            case ARecord a:
                Console.WriteLine($"A: {a.Address} (TTL: {a.InitialTimeToLive}s)");
                break;
            case AaaaRecord aaaa:
                Console.WriteLine($"AAAA: {aaaa.Address} (TTL: {aaaa.InitialTimeToLive}s)");
                break;
            case CNameRecord cname:
                Console.WriteLine($"CNAME: {cname.CanonicalName} (TTL: {cname.InitialTimeToLive}s)");
                break;
            case MxRecord mx:
                Console.WriteLine($"MX: {mx.Exchange} (Pref: {mx.Preference}, TTL: {mx.InitialTimeToLive}s)");
                break;
            case NsRecord ns:
                Console.WriteLine($"NS: {ns.NSDName} (TTL: {ns.InitialTimeToLive}s)");
                break;
            case TxtRecord txt:
                Console.WriteLine($"TXT: {string.Join(" ", txt.Text)} (TTL: {txt.InitialTimeToLive}s)");
                break;
            default:
                Console.WriteLine($"{dnsRecord}");
                break;
        }
    }
}

// Query each type
await QueryAndPrint(QueryType.A);
await QueryAndPrint(QueryType.AAAA);
await QueryAndPrint(QueryType.CNAME);
await QueryAndPrint(QueryType.MX);
await QueryAndPrint(QueryType.NS);
await QueryAndPrint(QueryType.TXT);

Conclusion

With just a few lines of C# and the powerful DnsClient.NET library, you can build a versatile DNS lookup tool. Whether you're troubleshooting, monitoring, or integrating into larger applications, this console app gives you a solid foundation.

Feel free to experiment, extend, and customize it to fit your needs!