如何正確發出 http web GET 請求

Question

我還是 C# 新手，我正在嘗試為此頁面創建一個應用程序，當我收到通知（已回答、評論等）時會告訴我。 但現在我只是想對 api 進行一個簡單的調用，它將獲取用戶的數據。

我正在使用 Visual Studio express 2012 構建 C# 應用程序，其中（現在）您輸入您的用戶 ID，因此應用程序將使用用戶 ID 發出請求並顯示該用戶 ID 的統計信息。

這是我嘗試提出請求的代碼：

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;
        }
    }
}

該類是一個對象，只需解析用戶 ID 並發出請求即可從表單訪問它。

我已經嘗試了許多我在谷歌上看過的例子，但不知道為什么我會收到這條消息“ ”。

我是這種算法的新手，如果有人可以分享一本書或教程來展示如何做這種事情（解釋每一步），我將不勝感激

Answer 1

服務器有時會壓縮它們的響應以節省帶寬，當發生這種情況時，您需要在嘗試讀取響應之前解壓縮響應。 幸運的是，.NET 框架可以自動執行此操作，但是，我們必須打開該設置。

這是一個如何實現這一目標的示例。

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();
    }
}

---

獲取異步

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();
    }
}

---

郵政
如果您希望使用 PUT、DELETE、ETC 等其他 HTTP 方法，則包含參數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();
    }
}

    

---

POST 異步
如果您希望使用 PUT、DELETE、ETC 等其他 HTTP 方法，則包含參數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();
    }
}

Answer 2

另一種方法是像這樣使用“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();
        }
    }
}

檢查的HttpClient VS HttpWebRequest的距離計算器以及這種從其他。

2020 年 6 月 22 日更新：不建議在“使用”塊中使用 httpclient，因為它可能會導致端口耗盡。

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 .Net Core 2.1+，請考慮使用IHttpClientFactory並在啟動代碼中像這樣注入。

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

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

Answer 3

我的意見最簡單的方式

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

或者

 var bytes = web.DownloadData(url);

Answer 4

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();
    }
}

Answer 5

添加到已經給出的響應中，這是一個完整的示例，訪問JSON PlaceHolder站點。

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;
        }
    }
}