Web service token authentication

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Services;
using System.Web.Services.Protocols;
using System.Text;

namespace AuthWebApplication
{
    using System.Security.Cryptography;

    /// <summary>
    /// Summary description for WebService1
    /// </summary>
    [WebService(Namespace = "http://tempuri.org/")]
    [WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
    [System.ComponentModel.ToolboxItem(false)]
    // To allow this Web Service to be called from script, using ASP.NET AJAX, uncomment the following line.
    // [System.Web.Script.Services.ScriptService]
    public class WebService1 : System.Web.Services.WebService
    {
        public WebService1 ()
        {

        //Uncomment the following line if using designed components
        //InitializeComponent();
        }
        //public AuthHeader SoapAuthentication;

        [WebMethod(Description = "A sample Web Method to demonstrate a simple web Service Authentication using SOAP Headers")]
        public string SampleWebMethod(string Username,String Password)
        {

       if (Username == "demo" && Password == "123")
       {
              return Username + " is an Authenticated User to access the Web Method";
       }
      else
     {
           return "Access Denied for " + Username;
       }

}