Multiview and custom validators not firing

I have a custom validator in a second view but it is not fired when the page is submitted.

I load the page with a multiview containing two views. When the page loads, the first view is shown. Then I press a button and the second view is shown but when the data is submitted, it seems that the validators are not active.

Any logic or explanation?

There is no problem is the second view is shown from the beginning.

Example:



------------
ASPX.CS
------------
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

public partial class _Default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        MultiView1.SetActiveView(View1);
    }
    protected void ImageButton1_Click(object sender, ImageClickEventArgs e)
    {
        MultiView1.SetActiveView(View2);
    }
    protected void CustomValidator1_ServerValidate(object source, ServerValidateEventArgs args)
    {
        args.IsValid = false;
    }
    protected void Button1_Click(object sender, EventArgs e)
    {
        if (Page.IsValid)
        {
            TextBox1.Text = "OK";
        }
        else
        {
            TextBox1.Text = "NO";
        }

    }
}

------------
ASPX
------------
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>





   


   

   

       
           
                                    onclick="ImageButton1_Click" />
           
           
               
                                    ControlToValidate="TextBox1" ErrorMessage="CustomValidator"
                    onservervalidate="CustomValidator1_ServerValidate">
               

               

                                    UseSubmitBehavior="False" />