Updating Page Elements in Events

The easiest way to dynamically update a page within File Upload event handlers is to use the AJAX controls included in the PowerWEB LiveControls for ASP.NET product. For more information on LiveControls, click here.

It is usually possible to update other page elements by decorating them with the following attribute:

LiveControlUpdate="true"

One notable exception to this is a control's Visible property. Unfortunately, updating this property does not work, even with the LiveControlUpdate attribute.
Instead, you can place the control in a div tag, give it an id and set its display to "none."
For example, to show a Panel:

<div id="panelDiv" style="display:none">
  <asp:Panel ID="Panel1" runat="server" LiveControlUpdate="true" BackColor="#C00000" ForeColor="White" Height="50px" Width="125px">
  </asp:Panel>
</div>

Then, in the event, set its display to "inline":

Upload1.BufferedScript.Write("document.getElementById('panelDiv').style.display='inline';");