Cancel DNS.BeginGetHostEntry

DnsLookup.cs

using System;
using System.Net;
using System.Threading.Tasks;

namespace DnsLookup
{
    class Program
    {
        static void Main(string[] args)
        {
            ResolveTest("asdfasdfasdfasdfasdfa.ca", 15);
            ResolveTest("google.com", 15);
            RunTest();
            Console.ReadLine();
        }

        public static async void RunTest()
        {
            await Resolve("asdfasdfasdfasdfasdfa.ca", 60);
            await Resolve("google.com", 60);
        }

        public static Task<IPHostEntry> GetHostEntryAsync(string hostNameOrAddress)
        {
            return Task<IPHostEntry>.Factory.FromAsync<string>(new Func<string, AsyncCallback, object, IAsyncResult>(Dns.BeginGetHostEntry), new Func<IAsyncResult, IPHostEntry>(Dns.EndGetHostEntry), hostNameOrAddress, null);
        }

        public static bool ResolveTest(string hostNameOrAddress, int millisecond_time_out)
        {
            ResolveState ioContext = new ResolveState(hostNameOrAddress);
            var result = Dns.BeginGetHostEntry(ioContext.HostName, null, null);
            var success = result.AsyncWaitHandle.WaitOne(TimeSpan.FromMilliseconds(millisecond_time_out), true);
            if (!success)
            {
                ioContext.Result = ResolveType.Timeout;
            }
            else
            {
                try
                {
                    var ipList = Dns.EndGetHostEntry(result);
                    if (ipList == null || ipList.AddressList == null || ipList.AddressList.Length == 0)
                        ioContext.Result = ResolveType.InvalidHost;
                    else
                        ioContext.Result = ResolveType.Completed;
                }
                catch
                {
                    ioContext.Result = ResolveType.InvalidHost;
                }
            }
            Console.WriteLine($"The result of ResolveTest for {ioContext.HostName} is {ioContext.Result}");
            return ioContext.Result == ResolveType.Completed;
        }

        public static Task<bool> Resolve(string hostNameOrAddress, int millisecond_time_out)
        {
            return Task.Run(async () =>
            {
                bool completed = false;
                var asCallBack = new AsyncCallback(ar =>
                {
                    ResolveState context = (ResolveState)ar.AsyncState;
                    if (context.Result == ResolveType.Pending)
                    {
                        try
                        {
                            var ipList = Dns.EndGetHostEntry(ar);
                            if (ipList == null || ipList.AddressList == null || ipList.AddressList.Length == 0)
                                context.Result = ResolveType.InvalidHost;
                            else
                                context.Result = ResolveType.Completed;
                        }
                        catch
                        {
                            context.Result = ResolveType.InvalidHost;
                        }
                    }
                    completed = true;
                });
                ResolveState ioContext = new ResolveState(hostNameOrAddress);
                var result = Dns.BeginGetHostEntry(ioContext.HostName, asCallBack, ioContext);
                int miliCount = 0;
                while (!completed)
                {
                    miliCount++;
                    if (miliCount >= millisecond_time_out)
                    {
                        result.AsyncWaitHandle.Close();
                        result = null;
                        ioContext.Result = ResolveType.Timeout;
                        break;
                    }
                    await Task.Delay(1);
                }
                Console.WriteLine($"The result of Resolve for {ioContext.HostName} is {ioContext.Result}");
                return ioContext.Result == ResolveType.Completed;
            });
        }

        public class ResolveState
        {
            public ResolveState(string hostName)
            {
                if (string.IsNullOrWhiteSpace(hostName))
                    throw new ArgumentNullException(nameof(hostName));
                _hostName = hostName;
            }

            readonly string _hostName;

            public ResolveType Result { get; set; } = ResolveType.Pending;

            public string HostName => _hostName;

        }

        public enum ResolveType
        {
            Pending,
            Completed,
            InvalidHost,
            Timeout
        }
    }
}

Result of the tests.

The result of asdfasdfasdfasdfasdfa.ca is InvalidHost
The result of google.com is Completed

Updated and added ResolveTest