void Uploader_FileUploaded(object sender, UploaderEventArgs args)
    {

        string ext=System.IO.Path.GetExtension(args.FileName.ToLower());
        string folder = "c:\\save\\default";
        switch (ext)
        {
            case ".pdf":
            case ".doc":
            case ".txt":
                folder = "c:\\save\\doc";
                break;
            case ".gif":
            case ".jpg":
            case ".png":
                folder = "c:\\save\\img";
                break;
            default:
                folder = "c:\\save\\default";
                break;
        }

        if (!Directory.Exists(folder))
            Directory.CreateDirectory(folder);
        string newpath = Path.Combine(folder, args.FileName);
        args.CopyTo(newpath);

      }