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详解C#中HttpClient的用法及相关问题的解决方法

作者:黑夜中的潜行者

相信大家在使用 HttpClient 的时候遇到过 远程主机强迫关闭了一个现有的连接 的错误。本文就来说说它的解决方法以及HttpClient的正确用法,需要的可以参考一下

1、遇到的问题

① 远程主机强迫关闭了一个现有的连接

相信大家在使用 HttpClient 的时候遇到过 远程主机强迫关闭了一个现有的连接 的错误,一般的解决方法就是下面这种

解决办法:在请求方法中指定 ServicePoint 安全协议

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

② POST请求某种情况下请求会失败的解决方案

工作中遇到写正常的 http post 请求会失败的问题,于是就在原有的基础上改动了写代码使用HttpRequestMessage 指定 标头、HTTP 谓词和潜在数据,详情见代码第二个 post 请求方法。

2、使用HttpClient为什么建议使用单例

HttpClient 旨在被实例化一次并在应用程序的整个生命周期中重复使用。为每个请求实例化一个 HttpClient 类将耗尽重负载下可用的套接字数量。将导致 SocketException 错误。

3、基础代码实现

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请求
        /// </summary>
        /// <param name="url">请求地址</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请求
        /// </summary>
        /// <param name="url">请求地址</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请求
        /// </summary>
        /// <remarks>
        /// 用于非正常http请求
        /// </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对象转换为uri网址参数形式
        /// </summary>
        /// <param name="obj">Model对象</param>
        /// <param name="url">前部分网址</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()));//将字符串转换为它的转义表示形式,HttpUtility.UrlEncode是小写
                sb.Append("&");
            }
            sb.Remove(sb.Length - 1, 1);

            return sb.ToString();
        }
    }
}

到此这篇关于详解C#中HttpClient的用法及相关问题的解决方法的文章就介绍到这了,更多相关C# HttpClient内容请搜索脚本之家以前的文章或继续浏览下面的相关文章希望大家以后多多支持脚本之家!

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