WebBrower使用 Http 代理访问网页

public struct Struct_INTERNET_PROXY_INFO
        {
            public int dwAccessType;
            public IntPtr proxy;
            public IntPtr proxyBypass;
        };
        [DllImport("wininet.dll", SetLastError = true)]
        private static extern bool InternetSetOption(IntPtr hInternet, int dwOption, IntPtr lpBuffer, int lpdwBufferLength);
        private void RefreshIESettings(string strProxy)
        {
        const int INTERNET_OPTION_PROXY = 38;
        const int INTERNET_OPEN_TYPE_PROXY = 3; 

        Struct_INTERNET_PROXY_INFO struct_IPI; 

        // Filling in structure
        struct_IPI.dwAccessType = INTERNET_OPEN_TYPE_PROXY;
        struct_IPI.proxy = Marshal.StringToHGlobalAnsi(strProxy);
        struct_IPI.proxyBypass = Marshal.StringToHGlobalAnsi("local"); 

        // Allocating memory
        IntPtr intptrStruct = Marshal.AllocCoTaskMem(Marshal.SizeOf(struct_IPI)); 

        // Converting structure to IntPtr
        Marshal.StructureToPtr(struct_IPI, intptrStruct, true); 

        bool iReturn = InternetSetOption(IntPtr.Zero, INTERNET_OPTION_PROXY, intptrStruct, Marshal.SizeOf(struct_IPI));
        } 

        private void SomeFunc(string _ipAdd,string _url)
        {
            RefreshIESettings(_ipAdd);
            System.Object nullObject = 0;
            string strTemp = String.Empty;
            System.Object nullObjStr = strTemp;
            //webBrowser1.Navigate("http://www.7y8.com/V/ip.asp", null, null, null);
            webBrowser1.Navigate(_url, null, null, null);
            while (webBrowser1.ReadyState!=WebBrowserReadyState.Complete)
            {
                Application.DoEvents();
                System.Threading.Thread.Sleep(100);
            }
        }

　　PS:不知道从哪找来的了。