docker-sites-status-server/backend/SiteStatus/SiteStatus/Business/DnsBusiness.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Threading.Tasks;
using ARSoft.Tools.Net.Dns;
using SiteStatus.Dbo;

namespace SiteStatus.Business
{
    public class DnsBusiness
    {
        public async Task<DnsZoneStatusDbo> GetZoneStatusAsync(string zone, IEnumerable<string> servers)
        {
            var dnsStatus = new DnsZoneStatusDbo
            {
                Zone = zone,
                ServerStatus = new List<DnsZoneServerStatusDbo>()
            };

            foreach (var server in servers)
            {
                try
                {
                    var resolver = new DnsStubResolver(new []{IPAddress.Parse(server)});
                    var records = resolver.Resolve<SoaRecord>(zone, RecordType.Soa);
                    var record = records.FirstOrDefault();
                    dnsStatus.ServerStatus.Add(new DnsZoneServerStatusDbo
                    {
                        Server = server,
                        Soa = record?.ToString()
                    });
                }
                catch (Exception e)
                {
                    dnsStatus.ServerStatus.Add(new DnsZoneServerStatusDbo
                    {
                        Server = server,
                        Soa = null
                    });
                }
            }

            return dnsStatus;
        }
    }
}