File upload control not showing file path

 Hi.
I have used file upload control for upload files. For attach files i used asp:Button control.(button is at inside ajax update panel)

My problem is WHEN I CLICK ON BUTTON it not getting any attachment file(its always null). Same code i used with link button . meantime it getting and displaying attach file and it details.

anybody please let me know why its happening. This is my aspx.cs code.
Thanks
//string filename = "", savelocation = "";
        //string path = HttpContext.Current.Request.ApplicationPath;
        //try
        //{
        //    if (filemeasure.PostedFile.ContentLength > 0)
        //    {
        //    & ...