Ajax AsyncFileUpload fires server code but does not update client side - asp.net

Question

I have an asyncfileupload control inside an update panel.
In UploadedComplete, i save file to server.
protected void ImageFileUpload_UploadedComplete(object sender, AjaxControlToolkit.AsyncFileUploadEventArgs e)
{
System.Threading.Thread.Sleep(5000);
if (ImageFileUpload.HasFile)
{
Extension= System.IO.Path.GetExtension(ImageFileUpload.FileName);
TempImageUpload(ImageFileUpload.FileName.ToString(), Extension.Value);
FileImage.ImageUrl = "~/Temp/" + Session["ID"].ToString() + Extension.Value;
RemoveImageButton.Visible = true;
}
}
The file succesfully upload and fires the correct server side code.
But don't update viewstate and controls.
private string Extension
{
get {
if(ViewState["Extension"]==null)
return string.Empty;
else
return (string)ViewState["Extension"]; }
set { ViewState["Extension"] = value; }
}

Answer 1

I save file On UploadedComplete event.
protected void ImageFileUpload_UploadedComplete(object sender, AjaxControlToolkit.AsyncFileUploadEventArgs e)
{
if (ImageFileUpload.HasFile)
{
ImageFileUpload.SaveAs(Request.PhysicalApplicationPath + "Temp\\" + Session["ID"].ToString() + extension);
}
}
and fot change control in client side, i use OnClientUploadComplete.
function uploadComplete(sender, args) {
var filename = args.get_fileName();
document.getElementById('<%= Extension.ClientID %>').value = "." + filename.split('.').pop();
var btn = document.getElementById('<%= RemoveImageButton.ClientID %>')
btn.style.visibility = 'visible';
}