C# 设置代理

1.检查代理是否可用：

  /// <summary>
        ///  验证代理IP地址是否可用
       /// </summary>
       /// <param name="callback">是否可用</param>
       /// <param name="ip">地址</param>
       /// <param name="port">端口</param>
       public void ChecKedForIP(Action<bool> callback,string ip,int port,int timeout=0)
       {
           try
           {
               string Reshtml = string.Empty;//请求返回的结果
               WebProxy webproxy = new WebProxy(ip, port);  //实例代理设置
               HttpWebRequest Httpweq = (HttpWebRequest)WebRequest.Create("http://www.baidu.com");
               Httpweq.Proxy = webproxy;//模拟设置代理请求
               HttpWebResponse HttpRespon = (HttpWebResponse)Httpweq.GetResponse();
               Httpweq.Timeout = timeout != 0 ? timeout : 10000; //默认10秒，如果设置值，就用设置的值
               Encoding encoding = Encoding.GetEncoding("gb2312");//设置编码格式为汉字，防止英文系统，无法解码
               using (StreamReader reader = new StreamReader(HttpRespon.GetResponseStream(), encoding))
               {
                   Reshtml = reader.ReadToEnd().Trim();
                   if (!string.IsNullOrEmpty(Reshtml))
                   {
                       callback(true);
                   }
                   else
                   {
                       callback(false);
                   }
               }

           }
           catch (Exception)
           {

               callback(false);
           }
           finally { }
           
       }

 2.设置好恢复代理设置

[DllImport(@"wininet",SetLastError = true,CharSet = CharSet.Auto,EntryPoint = "InternetSetOption",CallingConvention = CallingConvention.StdCall)]
       public static extern bool InternetSetOption
       (
       int hInternet,
       int dmOption,
       IntPtr lpBuffer,
       int dwBufferLength
       );


       /// <summary>
       /// 设置代理
       /// </summary>
       /// <param name="ip_port">IP地址和端口</param>
       public void SetProxy(string ip_port)
       {
           //打开注册表
           RegistryKey regKey = Registry.CurrentUser;
           string SubKeyPath = @"Software\Microsoft\Windows\CurrentVersion\Internet Settings";
           RegistryKey optionKey = regKey.OpenSubKey(SubKeyPath, true);
           //更改健值，设置代理，
           optionKey.SetValue("ProxyEnable", 1);
           if (ip_port.Length == 0)
           {
               optionKey.SetValue("ProxyEnable", 0);
           }
           optionKey.SetValue("ProxyServer", ip_port);

           //激活代理设置
           InternetSetOption(0, 39, IntPtr.Zero, 0);
           InternetSetOption(0, 37, IntPtr.Zero, 0);
       }

       /// <summary>
       /// 不使用代理设置
       /// </summary>
       public void UnSetProxy()
       {
           RegistryKey regKey = Registry.CurrentUser;
           string SubKeyPath = @"Software\Microsoft\Windows\CurrentVersion\Internet Settings";
           RegistryKey optionKey = regKey.OpenSubKey(SubKeyPath, true);
           //更改健值，设置代理，
           optionKey.SetValue("ProxyEnable", 0);
           //激活代理设置
           InternetSetOption(0, 39, IntPtr.Zero, 0);
           InternetSetOption(0, 37, IntPtr.Zero, 0);
       }