I have an UpdatePanel which has an upload control and a button to upload. The button is set as a trigger, but the event handler for the button fails to execute on the first PostBack.
My ASPX code is:
<asp:UpdatePanel ID="updPages" runat="server" UpdateMode="Conditional">
<ContentTemplate>
<div class="
tabs">
<ul>
<li><asp:LinkButton ID="lnkContentsPages" runat="server" OnClick="updateContents" CommandArgument="pages">Pages</asp:LinkButton></li>
<%-- these
tabs change the ActiveViewIndex to show a different UserControl --%>
<li><asp:LinkButton ID="lnkContentsImages" runat="server" OnClick="updateContents" CommandArgument="images">Images</asp:LinkButton></li>
</ul>
<div class="tabbedContent">
<asp:MultiView runat="server" ID="mltContentsInner" ActiveViewIndex="0">
<asp:View ID="viwContentsImages" runat="server">
// ajax usercontrol for a list of images - works fine with ajax
<fieldset>
<legend>Upload New</legend>
<div class="formRow">
<asp:Label ID="lblFile" runat="server" Text="Filename" AssociatedControlID="uplFile" />
<asp:FileUpload ID="uplFile" runat="server" />
</div>
<div class="formRow">
<asp:Label ID="lblImageDescription" runat="server" Text="Description" AssociatedControlID="txtImageDescription" />
<asp:TextBox runat="server" ID="txtImageDescription" />
</div>
<asp:Button ID="btnUpload" runat="server" Text="Upload" CssClass="c3button btnUpload" CausesValidation="false" OnClick="btnUpload_Click" />
</fieldset>
</asp:View>
<asp:View ID="viwContentsPages" runat="server">
// ajax usercontrol - works fine with ajax
</asp:View>
</asp:MultiView>
</div>
</div>
</ContentTemplate>
<Triggers>
<asp:PostBackTrigger ControlID="btnUpload" />
</Triggers>
</asp:UpdatePanel>
The button works without fail on the second and subsequent times, just not the first. Is there any reason for this?
