[编程笔记] 未经处理的异常: System.Net.WebException: 基础连接已经关闭: 发送时发生错误。 ---> System.IO.IOException: 由于远程方已关 闭传输流，身份验证失败。

　　背景：.NET4.0的项目调用对方一个接口

　　核心代码：ServicePointManager.SecurityProtocol = (SecurityProtocolType)3072;

　　完整代码：

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net;
using System.Text;

namespace ConsoleApp1
{
    internal class Program
    {
        static void Main(string[] args)
        {
            var res = HttpGet("url");
            Console.WriteLine(res);
        }

        public static string HttpGet(string url)
        {
            ServicePointManager.SecurityProtocol = (SecurityProtocolType)3072;
            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
            request.Method = "GET";
            request.ContentType = "application/json;charset=UTF-8";
            request.Timeout = 15000;
            using (HttpWebResponse response = (HttpWebResponse)request.GetResponse())
            using (StreamReader reader = new StreamReader(response.GetResponseStream(), Encoding.UTF8))
            {
                var res = reader.ReadToEnd();
                return res;
            }
        }

    }
}