ASP.NET code for Upload and Download

if (FileUploadControl.HasFile)
              {
                  try
                  {
                      filename = Path.GetFileName(FileUploadControl.FileName);
                      FileUploadControl.SaveAs(Server.MapPath("~/Documents/LetterInward/") + filename);
                      objInwardLetter.strPath = "~/Documents/LetterInward/" + filename;
                      StatusLabel.Text = "Upload status: File uploaded!";

protected void lnkAttachment_Click(object sender, EventArgs e)
   {
       string filename = string.Empty;
       string path = "~/Documents/LetterInward/" + lblcurentFilePath.Text;
       if (lblcurentFilePath.Text != "")
       {
           if (path != "")
           {
               filename = (path).Remove(0, (path.LastIndexOf('/') + 1));
               System.IO.FileInfo file;
               file = new System.IO.FileInfo(Server.MapPath(path));
               Response.Clear();
               Response.ClearContent();
               Response.ClearHeaders();
               //Added later on 22-Nov-2011 because zip file not extracted at client side
               Response.Buffer = true;
               Response.AppendHeader("Content-Length", file.Length.ToString());
               Response.ContentType = GetMimeTypeByFileName(filename);
               Response.AppendHeader("Content-Disposition:", "attachment; filename=" + filename);
               Response.TransmitFile(file.FullName);
               Response.Flush();
               ApplicationInstance.CompleteRequest();
           }
       }
   }
   public string GetMimeTypeByFileName(string sFileName)
   {
       string sMime = "application/octet-stream";

       string sExtension = System.IO.Path.GetExtension(sFileName);
       if (!string.IsNullOrEmpty(sExtension))
       {
           sExtension = sExtension.Replace(".", "");
           sExtension = sExtension.ToLower();

           if (sExtension == "xls" || sExtension == "xlsx")
           {
               sMime = "application/ms-excel";
           }
           else if (sExtension == "doc" || sExtension == "docx")
           {
               sMime = "application/msword";
           }
           else if (sExtension == "ppt" || sExtension == "pptx")
           {
               sMime = "application/ms-powerpoint";
           }
           else if (sExtension == "rtf")
           {
               sMime = "application/rtf";
           }
           else if (sExtension == "zip")
           {
               sMime = "application/zip";
           }
           else if (sExtension == "mp3")
           {
               sMime = "audio/mpeg";
           }
           else if (sExtension == "bmp")
           {
               sMime = "image/bmp";
           }
           else if (sExtension == "gif")
           {
               sMime = "image/gif";
           }
           else if (sExtension == "jpg" || sExtension == "jpeg")
           {
               sMime = "image/jpeg";
           }
           else if (sExtension == "png")
           {
               sMime = "image/png";
           }
           else if (sExtension == "tiff" || sExtension == "tif")
           {
               sMime = "image/tiff";
           }
           else if (sExtension == "txt")
           {
               sMime = "text/plain";
           }
       }
       return sMime;
   }