show a progress image while the pdf is downloading

 

 Hi:

I have an .aspx page which only shows a pretty large pdf file, the function works fine, however, since the pdf file size is about 3M, so it takes a while to show it on the page, now, I want to add a kind of progress image while the pdf is downloading, can you please give me some suggestion on how to create the progress function?

I just don't know when to show the progress image, and when hide it after the pdf is showing on page. Thanks a lot.

 JT

===========below is the only code in that aspx.cs page================

protected void Page_Load(object sender, EventArgs e)
    {
        Response.ClearContent();
        Response.ClearHeaders();
        Response.ContentType = "application/pdf";
        string filePath = ...