如何记录传出的 HttpClient 请求？

Question

我想连接到 REST Api，但无论我如何构建请求，它都会不断返回 status code 400 (Bad Request)。

HttpResponseMessage response = client.PostAsync(url, content).Result;

response.EnsureSuccessStatusCode();

我的问题是，如何调试我的https 请求到服务器？我想看看我的 HTTP 请求是什么样子的。

我尝试使用DiagnosticSource 类，因此我创建了Observer 类并为所有听众订阅它。

观察者

class Observer : IObserver<DiagnosticListener>
    {
        public void OnCompleted()
        {
            throw new NotImplementedException();
        }

        public void OnError(Exception error)
        {
            throw new NotImplementedException();
        }

        public void OnNext(DiagnosticListener value)
        {
            if (value.Name == "HttpHandlerDiagnosticListener")
            {
                value.Subscribe(new HttpClientObserver());
            }
        }
    }

HttpClientObserver

 class HttpClientObserver : IObserver<KeyValuePair<string, object>>
        {
            public void OnCompleted()
            {
                throw new NotImplementedException();
            }
    
            public void OnError(Exception error)
            {
                throw new NotImplementedException();
            }
    
            public void OnNext(KeyValuePair<string, object> value)
            {
                throw new NotImplementedException();
            }
        }

主要

static void Main(string[] args)
        {
            DiagnosticListener.AllListeners.Subscribe(new Diagnostic.Observer());

            // execute HttpClient methods do not throw any event to Observer

但是没有捕获到任何事件。我错过了什么，HttpClient 是否支持DiagnosticSource（我如何识别哪些课程？）。我还可以使用什么其他解决方案？

Answer 1

当您订阅侦听器时，您将创建一个类的新实例。您应该做的是创建一个私有只读实例。 DiagnosticListener 仅限于捕获 HTTP 客户端请求的开始和结束。

下面是一个基本的例子，（代码略有重构）

public static async Task Main(string[] args)
{
    var observer = new HttpClientGlobalListener();

    using (var subscription = DiagnosticListener.AllListeners.Subscribe(observer))
    {
        var results = await GetMyResultsAsync();
        Console.WriteLine(results);
    }
}

public static async Task<string> GetMyResultsAsync()
{
    var queryString = new StringContent("");

    using (HttpClient client = new HttpClient())
    {
        HttpResponseMessage response = await client.PostAsync(new Uri("https://example/"), queryString);
        //var json = JsonConvert.SerializeObject(response); // You could log response before raising error with "EnsureSuccessStatusCode".

        response.EnsureSuccessStatusCode();
        string responseBody = await response.Content.ReadAsStringAsync();
        return responseBody;
    }
}

public class HttpClientGlobalListener : IObserver<DiagnosticListener>
{
    private readonly HttpClientInterceptor _interceptor = new HttpClientInterceptor();

    public void OnCompleted() { }

    public void OnError(Exception error) { }

    public void OnNext(DiagnosticListener listener)
    {
        listener.Subscribe(_interceptor);
    }
}

public class HttpClientInterceptor : IObserver<KeyValuePair<string, object>>
{
    public void OnCompleted() { }

    public void OnError(Exception error) { }

    public void OnNext(KeyValuePair<string, object> value)
    {
        if (value.Key == "System.Net.Http.Desktop.HttpRequestOut.Start")
        {
            var requestObj = JsonConvert.SerializeObject(value.Value);
            Debug.WriteLine($"Request: {requestObj}");
        }
        else if (value.Key == "System.Net.Http.Desktop.HttpRequestOut.Stop")
        {
            var requestObj = JsonConvert.SerializeObject(value.Value);
            Debug.WriteLine($"Response: {requestObj}");
        }
    }
}