gistfile1.cs

 public class BasicAuth : IHttpModule
    {
        protected bool IsHeaderPresent
        {
            get
            {
                var context = HttpContext.Current;
                var authHeader = context.Request.Headers["Authorization"];
                return (!string.IsNullOrEmpty(authHeader));
            }
        }

        #region IHttpModule Members

        public void Init(HttpApplication context)
        {
            context.AuthenticateRequest += Check;
            context.EndRequest += EndRequest;
        }

        public void Dispose()
        {
        }

        #endregion

        void EndRequest(object sender, EventArgs e)
        {
            if (HttpContext.Current.Response.StatusCode == 401)
                SendAuthHeader();
        }

        void SendAuthHeader()
        {
            var context = HttpContext.Current;

            context.Response.StatusCode = 401;
            context.Response.AddHeader("WWW-Authenticate", string.Format("Basic realm=\"hardcoded\""));
        }


        void Check(object sender, EventArgs e)
        {
            if (!AuthenticateUser())
                DenyAccess();
        }

        void DenyAccess()
        {
            var context = HttpContext.Current;
            context.Response.StatusCode = 401;
            context.Response.End();
        }

        bool AuthenticateUser()
        {
            IDictionary<string, string> users = new Dictionary<string, string>()
                                                    {
                                                        { "magic", "socks" }
                                                    };

            var authHeader = HttpContext.Current.Request.Headers["Authorization"];

            if (authHeader != null && authHeader.StartsWith("Basic"))
            {
                // Extract credentials from header
                var credentials = ExtractCredentials(authHeader);
                var username = credentials[0];
                var password = credentials[1];

                if (users.ContainsKey(username) && users[username] == password)
                {
                    SetPrincipal(username);
                    return true;
                }
            }

            return false;
        }

        // Create GenericPrincipal and set it on Context.User
        static void SetPrincipal(string username)
        {
            //Create Principal and set Context.User
            var id = new GenericIdentity(username, "BasicAuth");
            var p = new GenericPrincipal(id, null);
            HttpContext.Current.User = p;
        }

        string[] ExtractCredentials(string authHeader)
        {
            // Strip out the "basic"
            var encodedUserPass = authHeader.Substring(6).Trim();

            // That's the right encoding
            var encoding = Encoding.GetEncoding("iso-8859-1");
            var userPass = encoding.GetString(Convert.FromBase64String(encodedUserPass));
            var separator = userPass.IndexOf(':');

            var credentials = new string[2];
            credentials[0] = userPass.Substring(0, separator);
            credentials[1] = userPass.Substring(separator + 1);

            return credentials;
        }
    }