alert if no data present in database

private void BindGridData()
    {
        try
        {
            con.Open();
            string menuid = Application["MenuId"].ToString();
            {
                string sql = "select * from rsa_ProductItemTable where MenuId=" + menuid;
                SqlCommand cmd = new SqlCommand(sql, con);
                SqlDataAdapter da = new SqlDataAdapter(sql, con);
                DataSet ds = new DataSet();
                da.Fill(ds);
                DataList1.DataSource = ds;
                DataList1.DataBind();
                }
            }

        catch (Exception ex)
        {
        }
        finally
        {
            con.Close();
        }
        }