如何发出HTTP POST Web请求

Canonical
如何使用该 方法发出HTTP请求并发送一些数据POST ？

我可以GET提出请求，但是我不知道如何提出POST请求。

有几种执行HTTP GET和POST请求的方法：

方法A：HttpClient（首选）

可用：.NET Framework 4.5+，.NET Standard 1.1+，.NET Core 1.0+。

目前，它是首选方法，并且具有异步性和高性能。在大多数情况下，请使用内置版本，但对于非常旧的平台，则提供了NuGet软件包。

using System.Net.Http;

设定

建议HttpClient在应用程序的生命周期中实例化一个实例，并共享它，除非您有特殊原因不这样做。

private static readonly HttpClient client = new HttpClient();

请参阅HttpClientFactory以获取依赖项注入解决方案。

• POST

  var values = new Dictionary<string, string>
  {
      { "thing1", "hello" },
      { "thing2", "world" }
  };
  
  var content = new FormUrlEncodedContent(values);
  
  var response = await client.PostAsync("http://www.example.com/recepticle.aspx", content);
  
  var responseString = await response.Content.ReadAsStringAsync();

• GET

  var responseString = await client.GetStringAsync("http://www.example.com/recepticle.aspx");

方法B：第三方库

RestSharp

• POST

   var client = new RestClient("http://example.com");
   // client.Authenticator = new HttpBasicAuthenticator(username, password);
   var request = new RestRequest("resource/{id}");
   request.AddParameter("thing1", "Hello");
   request.AddParameter("thing2", "world");
   request.AddHeader("header", "value");
   request.AddFile("file", path);
   var response = client.Post(request);
   var content = response.Content; // Raw content as string
   var response2 = client.Post<Person>(request);
   var name = response2.Data.Name;

Flurl.Http

这是一个更新的库，具有流畅的API，测试助手，在后台使用HttpClient且可移植。可通过NuGet获得。

    using Flurl.Http;

• POST

  var responseString = await "http://www.example.com/recepticle.aspx"
      .PostUrlEncodedAsync(new { thing1 = "hello", thing2 = "world" })
      .ReceiveString();

• GET

  var responseString = await "http://www.example.com/recepticle.aspx"
      .GetStringAsync();

方法C：HttpWebRequest（不建议用于新工作）

可用：.NET Framework 1.1+，.NET Standard 2.0+，.NET Core 1.0+。在.NET Core中，它主要是出于兼容性的考虑-它包装HttpClient，性能较低且不会获得新功能。

using System.Net;
using System.Text;  // For class Encoding
using System.IO;    // For StreamReader

• POST

  var request = (HttpWebRequest)WebRequest.Create("http://www.example.com/recepticle.aspx");
  
  var postData = "thing1=" + Uri.EscapeDataString("hello");
      postData += "&thing2=" + Uri.EscapeDataString("world");
  var data = Encoding.ASCII.GetBytes(postData);
  
  request.Method = "POST";
  request.ContentType = "application/x-www-form-urlencoded";
  request.ContentLength = data.Length;
  
  using (var stream = request.GetRequestStream())
  {
      stream.Write(data, 0, data.Length);
  }
  
  var response = (HttpWebResponse)request.GetResponse();
  
  var responseString = new StreamReader(response.GetResponseStream()).ReadToEnd();

• GET

  var request = (HttpWebRequest)WebRequest.Create("http://www.example.com/recepticle.aspx");
  
  var response = (HttpWebResponse)request.GetResponse();
  
  var responseString = new StreamReader(response.GetResponseStream()).ReadToEnd();

方法D：WebClient（不建议用于新工作）

这是一个包装HttpWebRequest。与比较HttpClient。

可在：.NET Framework 1.1+，NET Standard 2.0+，.NET Core 2.0+

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

• POST

  using (var client = new WebClient())
  {
      var values = new NameValueCollection();
      values["thing1"] = "hello";
      values["thing2"] = "world";
  
      var response = client.UploadValues("http://www.example.com/recepticle.aspx", values);
  
      var responseString = Encoding.Default.GetString(response);
  }

• GET

  using (var client = new WebClient())
  {
      var responseString = client.DownloadString("http://www.example.com/recepticle.aspx");
  }

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);
}

MSDN有一个示例。

using System;
using System.IO;
using System.Net;
using System.Text;

namespace Examples.System.Net
{
    public class WebRequestPostExample
    {
        public static void Main()
        {
            // Create a request using a URL that can receive a post. 
            WebRequest request = WebRequest.Create("http://www.contoso.com/PostAccepter.aspx");
            // Set the Method property of the request to POST.
            request.Method = "POST";
            // Create POST data and convert it to a byte array.
            string postData = "This is a test that posts this string to a Web server.";
            byte[] byteArray = Encoding.UTF8.GetBytes(postData);
            // Set the ContentType property of the WebRequest.
            request.ContentType = "application/x-www-form-urlencoded";
            // Set the ContentLength property of the WebRequest.
            request.ContentLength = byteArray.Length;
            // Get the request stream.
            Stream dataStream = request.GetRequestStream();
            // Write the data to the request stream.
            dataStream.Write(byteArray, 0, byteArray.Length);
            // Close the Stream object.
            dataStream.Close();
            // Get the response.
            WebResponse response = request.GetResponse();
            // Display the status.
            Console.WriteLine(((HttpWebResponse)response).StatusDescription);
            // Get the stream containing content returned by the server.
            dataStream = response.GetResponseStream();
            // Open the stream using a StreamReader for easy access.
            StreamReader reader = new StreamReader(dataStream);
            // Read the content.
            string responseFromServer = reader.ReadToEnd();
            // Display the content.
            Console.WriteLine(responseFromServer);
            // Clean up the streams.
            reader.Close();
            dataStream.Close();
            response.Close();
        }
    }
}

这是发送/接收JSON格式数据的完整工作示例，我使用了Visual Studio 2013 Express Edition：

using System;
using System.Collections.Generic;
using System.Data;
using System.Data.OleDb;
using System.IO;
using System.Linq;
using System.Net.Http;
using System.Text;
using System.Threading.Tasks;
using System.Web.Script.Serialization;

namespace ConsoleApplication1
{
    class Customer
    {
        public string Name { get; set; }
        public string Address { get; set; }
        public string Phone { get; set; }
    }

    public class Program
    {
        private static readonly HttpClient _Client = new HttpClient();
        private static JavaScriptSerializer _Serializer = new JavaScriptSerializer();

        static void Main(string[] args)
        {
            Run().Wait();
        }

        static async Task Run()
        {
            string url = "http://www.example.com/api/Customer";
            Customer cust = new Customer() { Name = "Example Customer", Address = "Some example address", Phone = "Some phone number" };
            var json = _Serializer.Serialize(cust);
            var response = await Request(HttpMethod.Post, url, json, new Dictionary<string, string>());
            string responseText = await response.Content.ReadAsStringAsync();

            List<YourCustomClassModel> serializedResult = _Serializer.Deserialize<List<YourCustomClassModel>>(responseText);

            Console.WriteLine(responseText);
            Console.ReadLine();
        }

        /// <summary>
        /// Makes an async HTTP Request
        /// </summary>
        /// <param name="pMethod">Those methods you know: GET, POST, HEAD, etc...</param>
        /// <param name="pUrl">Very predictable...</param>
        /// <param name="pJsonContent">String data to POST on the server</param>
        /// <param name="pHeaders">If you use some kind of Authorization you should use this</param>
        /// <returns></returns>
        static async Task<HttpResponseMessage> Request(HttpMethod pMethod, string pUrl, string pJsonContent, Dictionary<string, string> pHeaders)
        {
            var httpRequestMessage = new HttpRequestMessage();
            httpRequestMessage.Method = pMethod;
            httpRequestMessage.RequestUri = new Uri(pUrl);
            foreach (var head in pHeaders)
            {
                httpRequestMessage.Headers.Add(head.Key, head.Value);
            }
            switch (pMethod.Method)
            {
                case "POST":
                    HttpContent httpContent = new StringContent(pJsonContent, Encoding.UTF8, "application/json");
                    httpRequestMessage.Content = httpContent;
                    break;

            }

            return await _Client.SendAsync(httpRequestMessage);
        }
    }
}

这里有一些非常好的答案。让我发布一种不同的方法来使用WebClient（）设置标题。我还将向您展示如何设置API密钥。

        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);

此解决方案仅使用标准.NET调用。

经测试：

• 在企业WPF应用程序中使用。使用async / await避免阻塞UI。
• 与.NET 4.5+兼容。
• 无参数测试（在幕后需要“ GET”）。
• 经过参数测试（在幕后需要“ POST”）。
• 经过标准网页（例如Google）的测试。
• 使用内部基于Java的Web服务进行了测试。

参考：

// Add a Reference to the assembly System.Web

码：

using System;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.Net;
using System.Net.Http;
using System.Threading.Tasks;
using System.Web;

private async Task<WebResponse> CallUri(string url, TimeSpan timeout)
{
    var uri = new Uri(url);
    NameValueCollection rawParameters = HttpUtility.ParseQueryString(uri.Query);
    var parameters = new Dictionary<string, string>();
    foreach (string p in rawParameters.Keys)
    {
        parameters[p] = rawParameters[p];
    }

    var client = new HttpClient { Timeout = timeout };
    HttpResponseMessage response;
    if (parameters.Count == 0)
    {
        response = await client.GetAsync(url);
    }
    else
    {
        var content = new FormUrlEncodedContent(parameters);
        string urlMinusParameters = uri.OriginalString.Split('?')[0]; // Parameters always follow the '?' symbol.
        response = await client.PostAsync(urlMinusParameters, content);
    }
    var responseString = await response.Content.ReadAsStringAsync();

    return new WebResponse(response.StatusCode, responseString);
}

private class WebResponse
{
    public WebResponse(HttpStatusCode httpStatusCode, string response)
    {
        this.HttpStatusCode = httpStatusCode;
        this.Response = response;
    }
    public HttpStatusCode HttpStatusCode { get; }
    public string Response { get; }
}

要不带任何参数的调用（在幕后使用“ GET”）：

 var timeout = TimeSpan.FromSeconds(300);
 WebResponse response = await this.CallUri("http://www.google.com/", timeout);
 if (response.HttpStatusCode == HttpStatusCode.OK)
 {
     Console.Write(response.Response); // Print HTML.
 }

要使用参数进行调用（在幕后使用“ POST”）：

 var timeout = TimeSpan.FromSeconds(300);
 WebResponse response = await this.CallUri("http://example.com/path/to/page?name=ferret&color=purple", timeout);
 if (response.HttpStatusCode == HttpStatusCode.OK)
 {
     Console.Write(response.Response); // Print HTML.
 }

到目前为止，我已经找到了简单的（单线，无错误检查，无等待响应的）解决方案：

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

请谨慎使用！

使用Windows.Web.Http命名空间时，对于POST而不是FormUrlEncodedContent，我们编写HttpFormUrlEncodedContent。响应也是HttpResponseMessage的类型。其余的就是Evan Mulawski写下的内容。

如果您喜欢流畅的API，则可以使用Tiny.RestClient。在NuGet上可用。

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>();

为什么这不完全是琐碎的？进行请求不是，尤其是不处理结果，并且似乎还涉及到一些.NET错误-请参阅HttpClient中的错误。GetAsync应该抛出WebException，而不是TaskCanceledException

我最终得到了这段代码：

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()); 
        }

    } catch (TaskCanceledException ex) {
        if (cts is object && ex.CancellationToken == cts.Token) {
            // a real cancellation, triggered by the caller
            return (false, WebExceptionStatus.RequestCanceled, null, ex.ToString());
        } else {
            // a web request timeout (possibly other things!?)
            return (false, WebExceptionStatus.Timeout, null, ex.ToString());
        }

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

这将执行GET或POST取决于是否postBuffer为null

如果成功为真，那么响应将在 ResponseAsString

如果成功为假，则可以检查WebExceptionStatus，HttpStatusCode然后ResponseAsString尝试找出问题所在。

在.net core中，您可以使用以下代码进行调用，在此我向该代码添加了一些额外的功能，以便可以使您的代码在代理之后并在具有网络凭据的情况下工作（如果有的话），在这里我还提到您可以更改的编码你的信息。希望以上内容能对您有所帮助，并为您提供编码方面的帮助。

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;
        }