problem with validation control in updatePanel control

Hi all,

I am missing a problem with validation control in updatePanel control:

I want to hide updatepanel control when page load. When click show button then updatepanel  control will show.

It show when I remove RequiredFieldValidator  control, and don't show when I add RequiredFieldValidator  control in updatepanel. But I want to validate data

Help me how to does it work?Please.

my code here:

default.aspx page:

<asp:ScriptManager ID="ScriptManager2" EnablePageMethods="true" runat="server"></asp:ScriptManager>

<asp:UpdatePanel ID="udpTest" runat="server" Visible="False">
    <ContentTemplate>
        Test <asp:Button ID="Button1" runat="server" Text="Button" /><asp:TextBox ID="TextBox5" runat="server"></asp:TextBox>
       <asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server" ErrorMessage="RequiredFieldValidator"></asp:RequiredFieldValidator>
   </ContentTemplate>
</asp:UpdatePanel>

<asp:Button ID="btnShow" CssClass="btn btn-info" runat="server" Text="Show" OnClick="btnDatHang_Click" />

and code behind default.cs:

protected void btnShow_Click(object sender, EventArgs e)
{
     udpTest.Visible = true;
}