Validation problem when using update panel

Hello all, ive created the folllowing simple example to shouw you the error im getting when using validation with an update panel.

<%@ Page Language="C#" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "">

<script runat="server">

    protected void Button1_Click(object sender, EventArgs e)
        Label1.Text = TextBox1.Text;

    protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)


<html xmlns="" >
<head runat="server">
    <title>Untitled Page</title>
    <form id="form1" runat="server">
        <asp:ScriptManager ID="ScriptManager1" runat="server">
        <asp:UpdatePanel ID="UpdatePanel1" runat="server">
                <asp:TextBox ID="TextBox1" runat="server" Height="17px" Width="81px"></asp:TextBox>
                <asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server" ControlToValidate="TextBox1"
                    ErrorMessage="RequiredFieldValidator" ValidationGroup="TEST">*</asp:RequiredFieldValidator>
                <asp:DropDownList ID="DropDownList1" runat="server" OnSelectedIndexChanged="DropDownList1_SelectedIndexChanged" AutoPostBack="True">
                </asp:DropDownList><br />
                <asp:Button ID="Button1" runat="server" Text="Button" ValidationGroup="TEST" OnClick="Button1_Click" />
                <asp:AsyncPostBackTrigger ControlID="Button1" EventName="Click"/>
                <asp:AsyncPostBackTrigger ControlID="DropDownList1" EventName="SelectedIndexChanged"/>
        <asp:Label ID="Label1" runat="server" Text="Label"></asp:Label>

Whne the above page is loaded, if the button is clicked, the validation will appear. However, if I change the fropdown value first, then try clicking the button, the validation (*) will not appear.

Any ideas how to always get the validation to appear?

I have the same problem, sucks pretty much. anyone with a solution?

any ideas?

is it the same as using a fileupload within an upload panel? i.e. it will never work?

Hmm, try removing the validation group and see what happens.

ive removed the validation group, however still no luck :frowning:

Uhm, I just figured out this is a known issue. See this thread for details, and a solution.

Great stuff, its working now. thanks