c#设置取消ie代理服务器

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);
        public static bool RefreshIESettings(string strProxy)
        {
            const int INTERNET_OPTION_PROXY = 38;
            const int INTERNET_OPEN_TYPE_PROXY = 3;
            const int INTERNET_OPEN_TYPE_DIRECT = 1;
            Struct_INTERNET_PROXY_INFO struct_IPI;
            // Filling in structure
            if (string.IsNullOrEmpty(strProxy))
            {
                struct_IPI.dwAccessType = INTERNET_OPEN_TYPE_DIRECT;
            }
            else
            {
                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));

            return iReturn;
        }