请各位大虾指教一个问题！！

我想做一个登陆后，查询登录者在sql数据库里信息的页面，但老报错，应该怎么写比较好，本人初学菜鸟，求教！！谢谢




public partial class Default2 : System.Web.UI.Page
{

    protected void Page_Load(object sender, EventArgs e)
    {
        SqlConnection con = new SqlConnection("server=;database=contacts;uid=;pwd=;");
        con.Open();

        SqlCommand cmd = new SqlCommand("select count(*) from tb_gongzi where userName='" + Session["userName"].ToString() + "'");
        SqlDataReader sdr = cmd.ExecuteReader();
        if (sdr.Read())
        {
         
            this.lblUsername.Text = sdr["userName"].ToString();
            this.lblGongzi.Text = sdr["csGongzi"].ToString();
            this.lblKoukuan.Text = sdr["csJiaofei"].ToString();

        }
      
    }
}
ExecuteReader: Connection 属性尚未初始化。报这样的错！！
this.lblUsername.Text = sdr["userName"].ToString(); 也没有定义