Is it possible to set custom DNS resolver in C#'s HttpClient

Question

what exactly I want :

public static CustomDnsResolver : Dns 
{
   .....
}

public static void Main(string[] args) 
{
    var httpClient = new HttpClient();
    httpClient.Dns(new CustomDnsResolver());
}

basically I just want to use my custom DNS resolver in HttpClient instead of System default, Is there any way to achieve it?

Answer 1

The use case you have is exactly why Microsoft build the HttpClient stack. It allow you to put your business logic in layered class with the help of HttpMessageHandler class. You can find some sample in ms docs or visualstudiomagazine

void Main()
{
    var dnsHandler = new DnsHandler(new CustomDnsResolver());
    var client = new HttpClient(dnsHandler);
    var html = client.GetStringAsync("http://google.com").Result;
}

public class DnsHandler : HttpClientHandler
{
    private readonly CustomDnsResolver _dnsResolver;

    public DnsHandler(CustomDnsResolver dnsResolver)
    {
        _dnsResolver = dnsResolver;
    }

    protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
    {
        var host = request.RequestUri.Host;
        var ip = _dnsResolver.Resolve(host);

        var builder = new UriBuilder(request.RequestUri);
        builder.Host = ip;

        request.RequestUri = builder.Uri;

        return base.SendAsync(request, cancellationToken);
    }
}

public class CustomDnsResolver
{
    public string Resolve(string host)
    {
        return "127.0.0.1";
    }
}