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詳解C#中HttpClient的用法及相關(guān)問題的解決方法

更新時(shí)間：2022年11月18日 11:23:39 作者：黑夜中的潛行者

相信大家在使用 HttpClient 的時(shí)候遇到過遠(yuǎn)程主機(jī)強(qiáng)迫關(guān)閉了一個(gè)現(xiàn)有的連接的錯(cuò)誤。本文就來說說它的解決方法以及HttpClient的正確用法，需要的可以參考一下

1、遇到的問題

① 遠(yuǎn)程主機(jī)強(qiáng)迫關(guān)閉了一個(gè)現(xiàn)有的連接

相信大家在使用 HttpClient 的時(shí)候遇到過遠(yuǎn)程主機(jī)強(qiáng)迫關(guān)閉了一個(gè)現(xiàn)有的連接的錯(cuò)誤，一般的解決方法就是下面這種

解決辦法：在請求方法中指定 ServicePoint 安全協(xié)議

System.Net.ServicePointManager.SecurityProtocol = System.Net.SecurityProtocolType.Tls11 | System.Net.SecurityProtocolType.Tls12;

② POST請求某種情況下請求會失敗的解決方案

工作中遇到寫正常的 http post 請求會失敗的問題，于是就在原有的基礎(chǔ)上改動(dòng)了寫代碼使用HttpRequestMessage 指定標(biāo)頭、HTTP 謂詞和潛在數(shù)據(jù)，詳情見代碼第二個(gè) post 請求方法。

2、使用HttpClient為什么建議使用單例

HttpClient 旨在被實(shí)例化一次并在應(yīng)用程序的整個(gè)生命周期中重復(fù)使用。為每個(gè)請求實(shí)例化一個(gè) HttpClient 類將耗盡重負(fù)載下可用的套接字?jǐn)?shù)量。將導(dǎo)致 SocketException 錯(cuò)誤。

3、基礎(chǔ)代碼實(shí)現(xiàn)

using System;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Reflection;
using System.Text;

namespace Clear.DataServices.HttpHelper
{
    public class HttpClientService
    {
        private static HttpClientService _instance;

        private static readonly object _lock = new object();
        
        private static HttpClient _client;
        
        public HttpClientService() { }
        
        public static HttpClientService GetInstance()
        {
            if (_instance == null)
            {
                lock (_lock)
                {
                    if (_instance == null)
                    {
                        _instance = new HttpClientService();
                    }
                    
                    if (_client is null)
					{
					    _client = new HttpClient();
					}
                }
            }
            return _instance;
        }
      
        /// <summary>
        /// HttpClient Get請求
        /// </summary>
        /// <param name="url">請求地址</param>
        /// <returns></returns>
        public string HttpGet(string url)
        {
            try
            {
                if (_client.BaseAddress is null)
				{
				    _client.BaseAddress = new Uri(url);
				}
              
                client.DefaultRequestHeaders.Accept.Clear();
                HttpResponseMessage response = client.GetAsync(url).Result;

                response.EnsureSuccessStatusCode();
                string responseBody = response.Content.ReadAsStringAsync().Result;

                return responseBody;                
            }
            catch (Exception e)
            {                
                object errorMessage = new
                {
                    code = "-1",
                    message = e.Message
                };
                return JsonConvert.SerializeObject(errorMessage);
            }
        }

        /// <summary>
        /// HttpClient Post請求
        /// </summary>
        /// <param name="url">請求地址</param>
        /// <param name="content">HttpContent</param>
        /// <returns></returns>
        public string HttpPost(string url, string content, string token = null)
        {
            try
            {
                if (_client.BaseAddress is null)
				{
				    _client.BaseAddress = new Uri(url);
				}
				
                // System.Net.ServicePointManager.SecurityProtocol = System.Net.SecurityProtocolType.Tls11 | System.Net.SecurityProtocolType.Tls12;

                client.DefaultRequestHeaders.Accept.Clear();
                client.DefaultRequestHeaders.Connection.Add("keep-alive");
                if (!token.IsNullOrEmpty())
                {
                    client.DefaultRequestHeaders.Add("Authorization-Token", token);
                }
                client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
             
                HttpResponseMessage response = client.PostAsync(url, new StringContent(content, Encoding.UTF8, "application/json")).Result;
                response.EnsureSuccessStatusCode();
                string responseBody = response.Content.ReadAsStringAsync().Result;
             
                return responseBody;                
            }
            catch (Exception e)
            {                
                object errorMessage = new
                {
                    code = "-1",
                    message = e.Message
                };
                return JsonConvert.SerializeObject(errorMessage);
            }
        }

        /// <summary>
        /// HttpClient Post請求
        /// </summary>
        /// <remarks>
        /// 用于非正常http請求
        /// </remarks>
        /// <param name="url"></param>
        /// <param name="content"></param>
        /// <returns></returns>
        public string HttpPost(string url, string content)
        {
            try
            {
                using (var request = new HttpRequestMessage(new HttpMethod("Post"), url))
                {
                    // System.Net.ServicePointManager.SecurityProtocol = System.Net.SecurityProtocolType.Tls11 | System.Net.SecurityProtocolType.Tls12;

                    request.Headers.TryAddWithoutValidation("Content-Type", "application/json");

                    request.Content = new StringContent(content);

                    request.Content.Headers.ContentType = MediaTypeHeaderValue.Parse("application/json");
                    var response = _client.SendAsync(request).Result;
                    return response.Content.ReadAsStringAsync().Result;
                }
            }
            catch (Exception e)
            {
                object errorMessage = new
                {
                    code = "-1",
                    message = e.Message
                };
                return JsonConvert.SerializeObject(errorMessage);
            }
        }

        /// <summary>
        /// Model對象轉(zhuǎn)換為uri網(wǎng)址參數(shù)形式
        /// </summary>
        /// <param name="obj">Model對象</param>
        /// <param name="url">前部分網(wǎng)址</param>
        /// <returns></returns>
        public string GetUriParam(object obj, string url = "")
        {
            PropertyInfo[] propertis = obj.GetType().GetProperties(BindingFlags.Instance | BindingFlags.Public);
            StringBuilder sb = new StringBuilder();
            sb.Append(url);
            sb.Append("?");
            foreach (var p in propertis)
            {
                var v = p.GetValue(obj, null);
                if (v == null) continue;

                sb.Append(p.Name);
                sb.Append("=");
                sb.Append(Uri.EscapeDataString(v.ToString()));//將字符串轉(zhuǎn)換為它的轉(zhuǎn)義表示形式，HttpUtility.UrlEncode是小寫
                sb.Append("&");
            }
            sb.Remove(sb.Length - 1, 1);

            return sb.ToString();
        }
    }
}

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