是否可以在 C# 的 HttpClient 中设置自定义 DNS 解析器 [英] Is it possible to set custom DNS resolver in C#'s HttpClient

问题描述

我到底想要什么:

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

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

基本上我只想在 HttpClient 中使用我的自定义 DNS 解析器而不是系统默认值，有什么办法可以实现吗?

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

推荐答案

您拥有的用例正是 Microsoft 构建 HttpClient 堆栈的原因.它允许您在 HttpMessageHandler 类的帮助下将业务逻辑放在分层类中.您可以在 ms docs 中找到一些示例 或 visualstudiomagazine

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";
    }
}

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