protected void btnAccess_Click(object sender, EventArgs e)
 {
     if (Page.IsValid)
     {
         string opass = System.Web.Security.FormsAuthentication.HashPasswordForStoringInConfigFile(txtCpass.Text, "SHA1");
         var oldpass = new ServiceReference1.Service1Client().Get_User_By_UserName_v2(Session["username"].ToString()).Password;
         if (opass != oldpass)
         {
             ScriptManager.RegisterStartupScript(this, GetType(), "Thông báo", "alert('Current Password is incorrect !!!');", true);
         }
         else
         {
             ServiceReference1.User user = new ServiceReference1.User();
             user.Username = Session["username"].ToString();
             string pass = System.Web.Security.FormsAuthentication.HashPasswordForStoringInConfigFile(txtNpass.Text, "SHA1");
             user.Password = pass;
             ServiceReference1.Service1Client sr = new ServiceReference1.Service1Client();
             if (sr.Update_Password(user) == 1)
             {
                 ScriptManager.RegisterStartupScript(this, GetType(), "Thông báo", "alert('Change successed !!!');", true);
                 Binding_data();
             }
             else
             {
                 ScriptManager.RegisterStartupScript(this, GetType(), "Thông báo", "alert('Error: Try again !!!');", true);
             }
         }
     }        
 }