You can't reload the page after a download and there is no way of knowing when the download completes or if the file is downloaded at all. You should instigate the download in a new tab, so if your download is a link then add target="_blank"
<a href="downloadfile.aspx?ID=123" target="_blank">download</a>
You could then reload the page on the click of that link. You haven't explained how you instigate the download so it's hard to give a specific solution.