C# IE代理操作

public class IPProxy
    {
        [System.Runtime.InteropServices.DllImport("wininet.dll", SetLastError = true)]
        private static extern bool InternetSetOption(IntPtr hInternet, int dwOption, IntPtr lPBuffer, int lpdwBufferLength);
        private const int INTERNET_OPTION_REFRESH = 0x000025;
        private const int INTERNET_OPTION_SETTINGS_CHANGED = 0x000027;

        public static bool Proxy(string ip,int port) {
            Microsoft.Win32.RegistryKey rk = Microsoft.Win32.Registry.CurrentUser.OpenSubKey(@"Software\Microsoft\Windows\CurrentVersion\Internet Settings", true);
            //设置代理可用 
            rk.SetValue("ProxyEnable", 1);
            //设置代理IP和端口 
            rk.SetValue("ProxyServer", string.Format("{0}:{1}", ip, port));
            rk.Close();
            //使它立即生效
            InternetSetOption(IntPtr.Zero, INTERNET_OPTION_SETTINGS_CHANGED, IntPtr.Zero, 0);
            InternetSetOption(IntPtr.Zero, INTERNET_OPTION_REFRESH, IntPtr.Zero, 0);
            if (IsUseful("http://www.baidu.com/")) {
                return true;
            }
            CancelProxy();
            return false;
        }
        public static void CancelProxy() {
            Microsoft.Win32.RegistryKey rk = Microsoft.Win32.Registry.CurrentUser.OpenSubKey(@"Software\Microsoft\Windows\CurrentVersion\Internet Settings", true);
            rk.SetValue("ProxyEnable", 0);
        }
        public static bool IsUseful(string ipOrHost) {
            using (System.Net.NetworkInformation.Ping pingSender = new System.Net.NetworkInformation.Ping())
            {
                
                try
                {

                    return System.Net.NetworkInformation.IPStatus.Success.Equals(pingSender.Send(ipOrHost,6000).Status);
                }
                catch {
                    return false;
                }
            }

        }
    }