页面是怎么知道用户通过了身份验证

 <configuration>
  <location  path="~/Default.aspx">
    <system.web>
      <authorization>
        <allow users="*"/>
      </authorization>
    </system.web>
  </location>
 <appSettings/>
 <connectionStrings/>
 <system.web>
  <authentication mode="Forms">
   <forms name="aa" loginUrl="Default.aspx" defaultUrl="Register.aspx" cookieless="UseUri"  slidingExpiration="true" timeout="20" enableCrossAppRedirects="false" protection="All">
    <credentials passwordFormat="Clear">
     <user name="aa" password="aa"/>
     <user name="=bb" password="bb"/>
    </credentials>
   </forms>
  </authentication>
    <authorization>
      <deny users="?"/>
      <allow users="*"/>
    </authorization>
    
      </system.web>
</configuration>

string  strsql= "server=(local);uid=sa;pwd=sa;database=GUOFENG";
        SqlConnection conn=new SqlConnection(strsql);
        conn.Open();
        string str = "select count(*) from Users where UsersName='" + this.TextBox2.Text + "'and PassWord='" + GetMD5( this.TextBox1.Text) + "'";
        SqlCommand comm = new SqlCommand(str,conn);
        int n = (int)comm.ExecuteScalar();
        if (n == 0)
           FormsAuthentication.RedirectFromLoginPage(this.TextBox2.Text, false);//就是这句话让程序判断是否通过验证的，如果写成下面的，就永远无法通过身份验证
            //Response.Redirect("~/Register.aspx");
        else
            HttpContext.Current.Response.Write("<script>alert('失败');</script>");