Javascript Alert Message from Code Behind in ASP.NET

public static void ShowAlertMessage(string error)
{

    Page page = HttpContext.Current.Handler as Page;
    if (page != null)
    {
        error = error.Replace("'", "\'");
        ScriptManager.RegisterStartupScript(page, page.GetType(), "err_msg", "alert('" + error + "');", true);
    }
}