.net 如何正确地发出http web GET请求

xeufq47z 于 2023-01-10 发布在 .NET

关注(0)|答案(5)|浏览(223)

我仍然是c#新手，我正在尝试为这个页面创建一个应用程序，它会告诉我何时收到通知（已应答，已评论等）。但现在我只是尝试对API进行一个简单的调用，它将获得用户的数据。
我正在使用Visual Studio Express 2012构建C#应用程序，（目前）您在其中输入您的用户ID，因此应用程序将使用用户ID发出请求，并显示此用户ID的统计信息。
下面是我尝试发出请求的代码：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
//Request library
using System.Net;
using System.IO;

namespace TestApplication
{
    class Connect
    {
        public string id;
        public string type;

        protected string api = "https://api.stackexchange.com/2.2/";
        protected string options = "?order=desc&sort=name&site=stackoverflow";

        public string request()
        {
            string totalUrl = this.join(id);

            return this.HttpGet(totalUrl);
        }

        protected string join(string s)
        {
            return api + type + "/" + s + options;
        }

        protected string get(string url)
        {
            try
            {
                string rt;

                WebRequest request = WebRequest.Create(url);

                WebResponse response = request.GetResponse();

                Stream dataStream = response.GetResponseStream();

                StreamReader reader = new StreamReader(dataStream);

                rt = reader.ReadToEnd();

                Console.WriteLine(rt);

                reader.Close();
                response.Close();

                return rt;
            }

            catch(Exception ex)
            {
                return "Error: " + ex.Message;
            }
        }
        public string HttpGet(string URI)
        {
            WebClient client = new WebClient();

            // Add a user agent header in case the 
            // requested URI contains a query.

            client.Headers.Add("user-agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.2; .NET CLR 1.0.3705;)");

            Stream data = client.OpenRead(URI);
            StreamReader reader = new StreamReader(data);
            string s = reader.ReadToEnd();
            data.Close();
            reader.Close();

            return s;
        }
    }
}

类是一个对象，并且通过仅解析用户ID并进行请求就可以从表单访问它。
我已经尝试了许多的例子，我已经在谷歌上看，但不知道为什么我得到了所有的方式这个消息“。
我是新的在这种算法，如果任何人可以分享一本书或教程，显示如何做这种东西（解释每一步），我会很感激

.net

来源：https://stackoverflow.com/questions/27108264/how-to-properly-make-a-http-web-get-request

5条答案

按热度按时间

6pp0gazn1#

如果使用**.NET 6**或更高版本，请阅读此答案底部的警告。
服务器有时候会压缩响应以保存带宽，当这种情况发生时，你需要在读取响应之前解压缩它。幸运的是，.NET框架可以自动完成这一操作，但是，我们必须打开该设置。
这里有一个例子可以说明如何实现这一点。

string html = string.Empty;
string url = @"https://api.stackexchange.com/2.2/answers?order=desc&sort=activity&site=stackoverflow";

HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
request.AutomaticDecompression = DecompressionMethods.GZip;

using (HttpWebResponse response = (HttpWebResponse)request.GetResponse())
using (Stream stream = response.GetResponseStream())
using (StreamReader reader = new StreamReader(stream))
{
    html = reader.ReadToEnd();
}

Console.WriteLine(html);

得到

public string Get(string uri)
{
    HttpWebRequest request = (HttpWebRequest)WebRequest.Create(uri);
    request.AutomaticDecompression = DecompressionMethods.GZip | DecompressionMethods.Deflate;

    using(HttpWebResponse response = (HttpWebResponse)request.GetResponse())
    using(Stream stream = response.GetResponseStream())
    using(StreamReader reader = new StreamReader(stream))
    {
        return reader.ReadToEnd();
    }
}

获取异步

public async Task<string> GetAsync(string uri)
{
    HttpWebRequest request = (HttpWebRequest)WebRequest.Create(uri);
    request.AutomaticDecompression = DecompressionMethods.GZip | DecompressionMethods.Deflate;

    using(HttpWebResponse response = (HttpWebResponse)await request.GetResponseAsync())
    using(Stream stream = response.GetResponseStream())
    using(StreamReader reader = new StreamReader(stream))
    {
        return await reader.ReadToEndAsync();
    }
}

邮寄

在您希望使用其他HTTP方法（如PUT、DELETE、ETC）的事件中包含参数method *

public string Post(string uri, string data, string contentType, string method = "POST")
{
    byte[] dataBytes = Encoding.UTF8.GetBytes(data);

    HttpWebRequest request = (HttpWebRequest)WebRequest.Create(uri);
    request.AutomaticDecompression = DecompressionMethods.GZip | DecompressionMethods.Deflate;
    request.ContentLength = dataBytes.Length;
    request.ContentType = contentType;
    request.Method = method;

    using(Stream requestBody = request.GetRequestStream())
    {
        requestBody.Write(dataBytes, 0, dataBytes.Length);
    }

    using(HttpWebResponse response = (HttpWebResponse)request.GetResponse())
    using(Stream stream = response.GetResponseStream())
    using(StreamReader reader = new StreamReader(stream))
    {
        return reader.ReadToEnd();
    }
}

异步后

在您希望使用其他HTTP方法（如PUT、DELETE、ETC）的事件中包含参数method *

public async Task<string> PostAsync(string uri, string data, string contentType, string method = "POST")
{
    byte[] dataBytes = Encoding.UTF8.GetBytes(data);

    HttpWebRequest request = (HttpWebRequest)WebRequest.Create(uri);
    request.AutomaticDecompression = DecompressionMethods.GZip | DecompressionMethods.Deflate;
    request.ContentLength = dataBytes.Length;
    request.ContentType = contentType;
    request.Method = method;

    using(Stream requestBody = request.GetRequestStream())
    {
        await requestBody.WriteAsync(dataBytes, 0, dataBytes.Length);
    }

    using(HttpWebResponse response = (HttpWebResponse)await request.GetResponseAsync())
    using(Stream stream = response.GetResponseStream())
    using(StreamReader reader = new StreamReader(stream))
    {
        return await reader.ReadToEndAsync();
    }
}

警告通知：此答案中概述的HTTP请求方法使用HttpWebRequest类，从.NET 6及更高版本开始，该类已弃用。对于依赖**.NET 6+**的环境，建议使用HttpClient，而此answer by DIG涵盖了该类。

参考：https://learn.microsoft.com/en-us/dotnet/core/compatibility/networking/6.0/webrequest-deprecated

赞(0）回复(0）举报 2023-01-10

wqsoz72f2#

另一种方法是像这样使用“HttpClient”：

using System;
using System.Net;
using System.Net.Http;

namespace Test
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Making API Call...");
            using (var client = new HttpClient(new HttpClientHandler { AutomaticDecompression = DecompressionMethods.GZip | DecompressionMethods.Deflate }))
            {
                client.BaseAddress = new Uri("https://api.stackexchange.com/2.2/");
                HttpResponseMessage response = client.GetAsync("answers?order=desc&sort=activity&site=stackoverflow").Result;
                response.EnsureSuccessStatusCode();
                string result = response.Content.ReadAsStringAsync().Result;
                Console.WriteLine("Result: " + result);
            }
            Console.ReadLine();
        }
    }
}

检查堆栈溢出中的HttpClient vs HttpWebRequest和其它堆栈中的this。

***2020年6月22日更新：***不建议在“using”块中使用httpclient，因为这可能导致端口耗尽。

private static HttpClient client = null;
    
ContructorMethod()
{
   if(client == null)
   {
        HttpClientHandler handler = new HttpClientHandler()
        {
            AutomaticDecompression = DecompressionMethods.GZip | DecompressionMethods.Deflate
        };        
        client = new HttpClient(handler);
   }
   client.BaseAddress = new Uri("https://api.stackexchange.com/2.2/");
   HttpResponseMessage response = client.GetAsync("answers?order=desc&sort=activity&site=stackoverflow").Result;
   response.EnsureSuccessStatusCode();
   string result = response.Content.ReadAsStringAsync().Result;
            Console.WriteLine("Result: " + result);           
 }

如果使用的是.Net Core 2.1+，请考虑使用IHttpClientFactory并在启动代码中这样注入。

var timeout = Policy.TimeoutAsync<HttpResponseMessage>(
            TimeSpan.FromSeconds(60));

 services.AddHttpClient<XApiClient>().ConfigurePrimaryHttpMessageHandler(() => new HttpClientHandler
        {
            AutomaticDecompression = DecompressionMethods.GZip | DecompressionMethods.Deflate
        }).AddPolicyHandler(request => timeout);

赞(0）回复(0）举报 2023-01-10

ntjbwcob3#

最简单的方式来表达我的意见

var web = new WebClient();
  var url = $"{hostname}/LoadDataSync?systemID={systemId}";
  var responseString = web.DownloadString(url);

或

var bytes = web.DownloadData(url);

赞(0）回复(0）举报 2023-01-10

jjhzyzn04#

var request = (HttpWebRequest)WebRequest.Create("sendrequesturl");
var response = (HttpWebResponse)request.GetResponse();
string responseString;
using (var stream = response.GetResponseStream())
{
    using (var reader = new StreamReader(stream))
    {
        responseString = reader.ReadToEnd();
    }
}

赞(0）回复(0）举报 2023-01-10

gk7wooem5#

添加到已经给出的响应，这是一个完整的例子击中JSON PlaceHolder网站。

using System;
using System.Net.Http;
using System.Threading.Tasks;
using Newtonsoft.Json;

namespace Publish
{
    class Program
    {
        static async Task Main(string[] args)
        {
            
            // Get Reqeust
            HttpClient req = new HttpClient();
            var content = await req.GetAsync("https://jsonplaceholder.typicode.com/users");
            Console.WriteLine(await content.Content.ReadAsStringAsync());

            // Post Request
            Post p = new Post("Some title", "Some body", "1");
            HttpContent payload = new StringContent(JsonConvert.SerializeObject(p));
            content = await req.PostAsync("https://jsonplaceholder.typicode.com/posts", payload);
            Console.WriteLine("--------------------------");
            Console.WriteLine(content.StatusCode);
            Console.WriteLine(await content.Content.ReadAsStringAsync());
        }
    }

    public struct Post {
        public string Title {get; set;}
        public string Body {get;set;}
        public string UserID {get; set;}

        public Post(string Title, string Body, string UserID){
            this.Title = Title;
            this.Body = Body;
            this.UserID = UserID;
        }
    }
}

赞(0）回复(0）举报 2023-01-10

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