HttpClient.GetAsync：基础连接已关闭：发送时发生意外错误

Question

这是我用来调用web API的代码。通过浏览器调用web api工作正常。

static void Main(string[] args)
{
    string url = "https://app1/api/AddUrl?longUrl=http://google.com";
    var result = GetTinyUrl(url).Result;
    Console.WriteLine(result.ShortUrl);     
}

protected static async Task<UrlResponse> GetUrl(string baseUrl)
{
    HttpClientHandler handler = new HttpClientHandler();
    handler.UseDefaultCredentials = true;

    var client = new HttpClient(handler);

    var response = client.GetAsync(baseUrl).Result;
    if (response.IsSuccessStatusCode)
    {
        HttpResponseMessage response1 = response;
        response.EnsureSuccessStatusCode();
        var resp = await response.Content.ReadAsStringAsync();
        var result = JsonConvert.DeserializeObject<UrlResponse>(resp);
        return result;
    }

    return null;
}

Answer 1

将.result阻塞调用与异步等待混合会导致死锁。

如果使用async await，则始终保持异步，并避免为每个调用创建HttpClient的新实例，因为这可能导致套接的耗尽。

static Lazy<HttpClient> http = new Lazy<HttpClient>(() => {
    //Handle TLS protocols
    System.Net.ServicePointManager.SecurityProtocol =
        System.Net.SecurityProtocolType.Tls
        | System.Net.SecurityProtocolType.Tls11
        | System.Net.SecurityProtocolType.Tls12;

    var handler = new HttpClientHandler() {
        UseDefaultCredentials = true
    };

    var client = new HttpClient(handler);
    return client;
});

protected static async Task<UrlResponse> GetUrl(string baseUrl) {
    var client = http.Value;

    var response = await client.GetAsync(baseUrl); //Remove .Result and just await
    if (response.IsSuccessStatusCode) {
        HttpResponseMessage response1 = response;
        response.EnsureSuccessStatusCode();
        var resp = await response.Content.ReadAsStringAsync();
        var result = JsonConvert.DeserializeObject<UrlResponse>(resp);
        return result;
    }
    return null;
}

由于这是一个控制台应用程序，并且只有一个线程调用异步，所以您必须更改在main中调用异步方法的方式

static void Main(string[] args) {
    string url = "https://app1/api/AddUrl?longUrl=http://google.com";
    var result = GetTinyUrl(url).GetAwaiter().GetResult(); //<-- 
    Console.WriteLine(result.ShortUrl);     
}