如何发出 HTTP POST 请求并在正文中发送数据？

网友回答：

简单的 GET 请求

using System.Net;

...

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

简单的开机自检请求

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);
}

网友回答：

有几种方法可以执行 HTTP GET 和 POST 请求：

方法 A：httpClient （首选）

在以下版本中可用：.NET Framework 4.5+、.NET Standard 1.1+ 和 .NET Core 1.0+。

它是当前首选的方法，并且是异步和高性能的。在大多数情况下使用内置版本，但对于非常旧的平台，有一个 NuGet 包。

using System.Net.Http;

设置

建议在应用程序的生存期内实例化一个并共享它，除非你有特定原因不这样做。HttpClient

private static readonly HttpClient client = new HttpClient();

有关依赖项注入解决方案，请参阅。HttpClientFactory

• 发布

    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();
  

• 获取

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

方法 B：第三方库

休息夏普

• 发布

     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

它是一个较新的库，具有流畅的API，测试助手，在引擎盖下使用HttpClient，并且是可移植的。它可通过 NuGet 获得。

    using Flurl.Http;

• 发布

    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（不推荐用于新工作）

在以下版本中可用：.NET Framework 1.1+、.NET Standard 2.0+、.NET Core 1.0+。在 .NET Core 中，它主要是为了兼容性 – 它包装 ，性能较低，并且不会获得新功能。HttpClient

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

• 发布

    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();
  

• 获取

    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：Web客户端（不推荐用于新工作）

这是一个包装器。儗。HttpWebRequestHttpClient

在以下版本中可用：.NET Framework 1.1+、NET Standard 2.0+ 和 .NET Core 2.0+。

在某些情况下（.NET Framework 4.5-4.8），如果需要同步执行 HTTP 请求，仍然可以使用。WebClient

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

• 发布

    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);
    }
  

• 获取

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

网友回答：

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();
        }
    }
}