这里有一些非常好的答案。让我发布一种不同的方法来设置你的头部与WebClient()。我还将向您展示如何设置API键。

        var client = new WebClient();
        string credentials = Convert.ToBase64String(Encoding.ASCII.GetBytes(userName + ":" + passWord));
        client.Headers[HttpRequestHeader.Authorization] = $"Basic {credentials}";
        //If you have your data stored in an object serialize it into json to pass to the webclient with Newtonsoft's JsonConvert
        var encodedJson = JsonConvert.SerializeObject(newAccount);

        client.Headers.Add($"x-api-key:{ApiKey}");
        client.Headers.Add("Content-Type:application/json");
        try
        {
            var response = client.UploadString($"{apiurl}", encodedJson);
            //if you have a model to deserialize the json into Newtonsoft will help bind the data to the model, this is an extremely useful trick for GET calls when you have a lot of data, you can strongly type a model and dump it into an instance of that class.
            Response response1 = JsonConvert.DeserializeObject<Response>(response);

如果你喜欢一个流畅的API，你可以使用Tiny.RestClient。在NuGet上可以买到。

var client = new TinyRestClient(new HttpClient(), "http://MyAPI.com/api");
// POST
var city = new City() { Name = "Paris", Country = "France" };
// With content
var response = await client.PostRequest("City", city)
                           .ExecuteAsync<bool>();

简单的GET请求

using System.Net;

...

using (var wb = new WebClient())
{
    var response = wb.DownloadString(url);
}

简单的POST请求

using System.Net;
using System.Collections.Specialized;

...

using (var wb = new WebClient())
{
    var data = new NameValueCollection();
    data["username"] = "myUser";
    data["password"] = "myPassword";

    var response = wb.UploadValues(url, "POST", data);
    string responseInString = Encoding.UTF8.GetString(response);
}

为什么这不是完全无关紧要的?执行请求并不是处理结果。而且似乎还涉及到一些。net Bug——参见HttpClient中的Bug。GetAsync应该抛出WebException，而不是TaskCanceledException

我最终得到了这样的代码:

static async Task<(bool Success, WebExceptionStatus WebExceptionStatus, HttpStatusCode? HttpStatusCode, string ResponseAsString)> HttpRequestAsync(HttpClient httpClient, string url, string postBuffer = null, CancellationTokenSource cts = null) {
    try {
        HttpResponseMessage resp = null;

        if (postBuffer is null) {
            resp = cts is null ? await httpClient.GetAsync(url) : await httpClient.GetAsync(url, cts.Token);

        } else {
            using (var httpContent = new StringContent(postBuffer)) {
                resp = cts is null ? await httpClient.PostAsync(url, httpContent) : await httpClient.PostAsync(url, httpContent, cts.Token);
            }
        }

        var respString = await resp.Content.ReadAsStringAsync();
        return (resp.IsSuccessStatusCode, WebExceptionStatus.Success, resp.StatusCode, respString);

    } catch (WebException ex) {
        WebExceptionStatus status = ex.Status;
        if (status == WebExceptionStatus.ProtocolError) {
            // Get HttpWebResponse so that you can check the HTTP status code.
            using (HttpWebResponse httpResponse = (HttpWebResponse)ex.Response) {
                return (false, status, httpResponse.StatusCode, httpResponse.StatusDescription);
            }
        } else {
            return (false, status, null, ex.ToString());
        }

    // https://devblogs.microsoft.com/dotnet/net-5-new-networking-improvements/
    } catch (TaskCanceledException ex) when (ex.InnerException is TimeoutException) {
        return (false, ex.ToString(), null, WebExceptionStatus.Timeout);

    } catch (TaskCanceledException ex) {
        return (false, ex.ToString(), null, WebExceptionStatus.RequestCanceled);

    } catch (Exception ex) {
        return (false, WebExceptionStatus.UnknownError, null, ex.ToString());
    }
}

这将根据postBuffer是否为空来执行GET或POST操作。

如果Success为true，响应将在ResponseAsString中。

如果Success为false，你可以检查WebExceptionStatus, HttpStatusCode和ResponseAsString，看看哪里出了问题。

在. net Core中，你可以用下面的代码进行POST调用。在这里，我为这段代码添加了一些额外的特性，这样您就可以让您的代码在代理后工作，如果有网络凭据的话。

在这里我还提到，您可以更改消息的编码。

HttpClient client = GetHttpClient(_config);

if (headers != null)
{
    foreach (var header in headers)
    {
        client.DefaultRequestHeaders.TryAddWithoutValidation(header.Key, header.Value);
    }
}

client.BaseAddress = new Uri(baseAddress);

Encoding encoding = Encoding.UTF8;

var result = await client.PostAsync(url, new StringContent(body, encoding, "application/json")).ConfigureAwait(false);
if (result.IsSuccessStatusCode)
{
    return new RequestResponse { severity = "Success", httpResponse = result.Content.ReadAsStringAsync().Result, StatusCode = result.StatusCode };
}
else
{
    return new RequestResponse { severity = "failure", httpResponse = result.Content.ReadAsStringAsync().Result, StatusCode = result.StatusCode };
}


public HttpClient GetHttpClient(IConfiguration _config)
{
    bool ProxyEnable = Convert.ToBoolean(_config["GlobalSettings:ProxyEnable"]);

    HttpClient client = null;
    if (!ProxyEnable)
    {
        client = new HttpClient();
    }
    else
    {
        string ProxyURL = _config["GlobalSettings:ProxyURL"];
        string ProxyUserName = _config["GlobalSettings:ProxyUserName"];
        string ProxyPassword = _config["GlobalSettings:ProxyPassword"];
        string[] ExceptionURL = _config["GlobalSettings:ExceptionURL"].Split(';');
        bool BypassProxyOnLocal = Convert.ToBoolean(_config["GlobalSettings:BypassProxyOnLocal"]);
        bool UseDefaultCredentials = Convert.ToBoolean(_config["GlobalSettings:UseDefaultCredentials"]);

        WebProxy proxy = new WebProxy
        {
            Address = new Uri(ProxyURL),
            BypassProxyOnLocal = BypassProxyOnLocal,
            UseDefaultCredentials = UseDefaultCredentials,
            BypassList = ExceptionURL,
            Credentials = new NetworkCredential(ProxyUserName, ProxyPassword)
        };

        HttpClientHandler handler = new HttpClientHandler { Proxy = proxy };
        client = new HttpClient(handler, true);
    }
    return client;
}

到目前为止，我找到了简单的解决方案(一行程序，没有错误检查，没有等待响应):

(new WebClient()).UploadStringAsync(new Uri(Address), dataString);‏

请谨慎使用!