webservice安全机制如何在ASP.NET中实现

using System;
using System.Web.Services;
using System.Web.Services.Protocols;

//请注意此命名空间必须有别于代理动态连接库上的命名空间。 
//否则，将产生诸如多处定义AuthHeader这样的错误。 
namespace SoapHeadersCS
{

  //由SoapHeader扩展而来的AuthHeader类 
  public class AuthHeaderCS : SoapHeader
  {
    public string Username;
    public string Password;
  }

  //[WebService(Description="用于演示SOAP头文件用法的简单示例")] 
  public class HeaderService
  {

    public AuthHeaderCS sHeader;

    [WebMethod(Description = "此方法要求有调用方自定义设置的soap头文件")]
    [SoapHeader("sHeader")]
    public string SecureMethod()
    {

      if (sHeader == null)
        return "ERROR:你不是VIP用户!";

      string usr = sHeader.Username;
      string pwd = sHeader.Password;

      if (AuthenticateUser(usr, pwd))
      {
        return "成功:" + usr + "," + pwd;
      }
      else
      {
        return "错误:未能通过身份验证";
      }
    }

    private bool AuthenticateUser(string usr, string pwd)
    {

      if ((usr != null) && (pwd != null))
      {
        return true;
      }
      return false;
    }
  }
}

WebService webservice = new WebService();
AuthHeaderCS auth = new AuthHeaderCS();
auth.Username = "vip";
auth.Password = "vippw";
webservice.AuthHeaderCSValue = auth;
textBox1.Text = webservice.SecureMethod();