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();
}
}
}
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