Nevermind, I got it:

 

<script runat="server">
    // Obtain the gallery folder from query string
    string album;
    void Page_Load(Object sender, EventArgs e)
    {
        album = Request.QueryString["album"];
        if (album == null || album=="/")
            gallery1.FolderPath = "106";
        gallery1.FolderPath = "~/DotNetGallery/" + album;
   }
</script>