WinHttpProxyWin32.cs

using System;
using System.Runtime.InteropServices;

namespace ProxySetup
{
    public abstract class WinHttpProxyWin32
    {
        /// <summary>
        /// WINHTTP_PROXY_INFO - structure supplied with WINHTTP_OPTION_PROXY to 
        /// get/set proxy information on a WinHttpOpen() handle
        /// </summary>
        [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
        public struct WINHTTP_PROXY_INFO
        {
            /// <summary>
            /// see WINHTTP_ACCESS_* types
            /// </summary>
            public WINHTTP_ACCESS_TYPES dwAccessType;

            /// <summary>
            /// proxy server list
            /// </summary>
            public string lpszProxy;

            /// <summary>
            /// proxy bypass list
            /// </summary>
            public string lpszProxyBypass;
        }

        /// <summary>
        /// WinHttpOpen dwAccessType values (also for WINHTTP_PROXY_INFO::dwAccessType)
        /// </summary>
        public enum WINHTTP_ACCESS_TYPES
        {
            WINHTTP_ACCESS_TYPE_DEFAULT_PROXY = 0,
            WINHTTP_ACCESS_TYPE_NO_PROXY = 1,
            WINHTTP_ACCESS_TYPE_NAMED_PROXY = 3
        }

        public const string WINHTTP_NO_PROXY_NAME = null;
        public const string WINHTTP_NO_PROXY_BYPASS = null;

        [DllImport("winhttp.dll", CharSet = CharSet.Unicode, SetLastError = true)]
        public static extern bool WinHttpSetDefaultProxyConfiguration(ref WINHTTP_PROXY_INFO info);

        [DllImport("winhttp.dll", CharSet = CharSet.Unicode, SetLastError = true)]
        public static extern bool WinHttpGetDefaultProxyConfiguration(ref WINHTTP_PROXY_INFO info);
    }
}