Created Issue: TabContainer incorrectly triggers validators [27111]

When the TabContainer is set to OnDemand = True and the TabPanel contains a validator like a requiredfieldvalidator then the validator will be triggered when the tab is activated although the form has not been submitted. You can recreate this issue using the following code:

<asp:TabContainer ID="TabContainer1" runat="server" ActiveTabIndex="0"
ondemand="True">
<asp:TabPanel runat="server" HeaderText="TabPanel1" ID="TabPanel1">
</asp:TabPanel>
<asp:TabPanel ID="TabPanel2" runat="server" HeaderText="TabPanel2">
</asp:TabPanel>
<asp:TabPanel ID="TabPanel3" runat="server" HeaderText="TabPanel3">
<ContentTemplate>
<asp:TextBox ID="TextBox1" runat="server" style="margin-bottom: 0px"
ValidationGroup="Test"></asp:TextBox>
<asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server"
ErrorMessage="RequiredFieldValidator" ControlToValidate="TextBox1"
ForeColor="Red" ValidationGroup="Test">*</asp:RequiredFieldValidator>
<asp:Button ID="Button1" runat="server" Text="Button" ValidationGroup="Test" />
</ContentTemplate>
</asp:TabPanel>
</asp:TabContainer>