How to determine the exception is a SQLException in Application_Error in global

In asp.net application, I'm trying to determine the exception of type SQLException so that if any db exception occurs we log error or so. I have following section in Global.asax.cs

void Application_Error(object sender, EventArgs e)
        {
            var _logger = LogManager.GetCurrentClassLogger();
            var ex = HttpContext.Current.Server.GetLastError();

            if (ex is HttpException)
            {
                if ((ex as HttpException).GetHttpCode() != 404)
                {
                    _logger.Fatal(ex, ex == null ? "" : ex.Message);
                }
            }
            else if (ex is type of SqlException )
            {
                _logger.Fatal(ex, ex == null ? "" : ex.Message);
            }
            else
            {
                _logger.Fatal(ex, ex == null ? "" : ex.Message);
            }