UpdatePanel not refreshing - asp.net

Question

I'm a newbie with ASP.NET, so probably my question is easy... but I'm wasting a lot of time with no success.
Part of my page is
<asp:UpdatePanel ID="pnlFileUpload" runat="server">
<ContentTemplate>
<ajaxToolkit:AsyncFileUpload ID="upload" runat="server" OnUploadedComplete="upload_UploadedComplete"
OnUploadedFileError="upload_UploadedFileError" UploaderStyle="Modern" UploadingBackColor="Yellow"
Width="400px" />
</ContentTemplate>
</asp:UpdatePanel>
<asp:UpdatePanel ID="pnlFileError" runat="server" UpdateMode="Conditional">
<ContentTemplate>
<asp:Label ID="lblFileError" runat="server" Text="errFile" Visible="false"></asp:Label>
</ContentTemplate>
<Triggers>
<asp:AsyncPostBackTrigger ControlID="upload" EventName="UploadedComplete" />
</Triggers>
</asp:UpdatePanel>
When user uploads (started with ajaxToolkit:AsyncFileUpload) ends, upload_UploadedComplete is called.
A sample code is:
protected void upload_UploadedComplete(object sender, AjaxControlToolkit.AsyncFileUploadEventArgs e)
{
int size = upload.PostedFile.ContentLength;
if (size > maxsize)
{
lblFileError.Text = 'File too big...';
lblFileError.ForeColor = System.Drawing.Color.Red;
lblFileError.Visible = true;
pnlFileError.Update();
}
}
But lblFileError is never shown... why?!?

Answer 1

AsyncFileupload doesn't need updatePanel ( none of AJAx toolkit controls need ) . as they have it as a built in . remove fileupload UpdatePanel and test again
:
it seems you can't do that in this way . based on AjaxControlToolkitSampleSite to show user a message about uploading file you should use "ScriptManager.RegisterClientScriptBlock" as below :
protected void upload_UploadedComplete(object sender, AjaxControlToolkit.AsyncFileUploadEventArgs e)
{
int size = upload.PostedFile.ContentLength;
if (size > maxsize)
{
ScriptManager.RegisterClientScriptBlock(this, this.GetType(), "error", "top.$get(\"" + lblFileError.ClientID + "\").innerHTML = 'File too big...';", true);
}
}