I haven't been able to use the modalpopupextender and panel. I removed the controls from my design page. However, I added code to the ViewFile click event:
protected void ViewFile(object sender, EventArgs e)
LinkButton lnk = (LinkButton)sender;
if (lnk != null)
string filePath = (sender as LinkButton).CommandArgument;
Response.AddHeader("content-disposition", "attachment; filename=" + Path.GetFileName(filePath) + ".pdf");
Response.WriteFile(Server.MapPath("~/Uploads/" + Path.GetFileName(filePath)));
When I click on the View link button, the .pdf file appears. I still would like to view it in a modalpopupextender or even an iframe.
I still welcome suggestions.