Invalid attempt to call Read when reader is closed.

public void root()
    {
        string user_sig, sig, categ, pkey;
        con.Open();
        SqlCommand cmd = new SqlCommand("select user_signature,signature,category,private_key from signature", con);
        SqlDataReader dr = cmd.ExecuteReader();
        if (dr.HasRows)
        {
            while (dr.Read())
            {
                user_sig = dr["user_signature"].ToString();
                sig = dr["signature"].ToString();
                categ = dr["category"].ToString();
                string result = "";
                string sig1 = categ;
                string num = sig1.Remove(1);
                Label1.Text = num;
                //Label2.Text = categ;
                switch(categ)
                {
                    case "11":
                       
                        if (con.State == ConnectionState.Closed)
                        {
                            con.Open();
                        }
                        dr.Close();
                        SqlCommand cmd1 = new SqlCommand("select distinct category from signature", con);
                        SqlDataReader dr1 = cmd1.ExecuteReader();
                        if (dr1.HasRows)
                        {
                            while (dr1.Read())
                            {
                                dr.Close();
                                string categ_sig = dr1["category"].ToString();
                                Label lblcateg = new Label();
                                lblcateg.Text = categ_sig;
                                this.Controls.Add(lblcateg);
                            }
                            dr1.Close();
                        }
                        dr1.Close();
                        con.Close();
                        break;
                
                    case "12":
                    Label lblcateg1 = new Label();
                    lblcateg1.Text = categ;
                    this.Controls.Add(lblcateg1);
                    break;
                    //dr1.Close();
                }
                
            }
            //dr.Close();
        }