displaying panel after selecting categories

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ASP.NET

i want to display different data in same panel after selecting different categories...when i select one category then it display data panel but after selecting another category it display same panel so whats wrong in coding ??????
my code is:-

protected void lbcategory_SelectedIndexChanged(object sender, EventArgs e)
    {

        SqlConnection sqlCon = new SqlConnection();
        sqlCon.ConnectionString = "Data Source=PC-13\\SQLEXPRESS;Initial Catalog=DbPlacementCoordinator;Integrated Security=True";
        sqlCon.Open();
        string str = lbcategory.SelectedItem.Value;
        string query = "Select Industry_ID from Industry_Category where Industry_Name=@str;";

        SqlCommand cmd3 = new SqlCommand(query, sqlCon);
        cmd3.Parameters.AddWithValue("str", str);
        int b = Convert.ToInt16(cmd3.ExecuteScalar());

        string jobcat = "Select Job_Name from Job_Category where Industry_ID=@b;";

        SqlCommand cmd4 = new SqlCommand(jobcat,sqlCon);
        //SqlDataReader reader = cmd.ExecuteReader();
        //cmd4.ExecuteNonQuery();
        //SqlCommand cmd4 = new SqlCommand();
        //cmd4.CommandType = CommandType.Text;
        //cmd4.CommandText = jobcategory;
        cmd4.Parameters.AddWithValue("b", b);
        //cmd4.Connection = sqlCon;
        SqlDataReader reader = cmd4.ExecuteReader();
        
        while (reader.Read())
        {
                //Label6.Text = Convert.ToString(reader[0]);
                //Label8.Text = Convert.ToString(reader[1]);
                //Label10.Text = Convert.ToString(reader[2]);
                //Label12.Text = Convert.ToString(reader[3]);
                //Label14.Text = Convert.ToString(reader[4]);
                //Label16.Text = Convert.ToString(reader[5]);
                //Label18.Text = Convert.ToString(reader[6]);
                //Label20.Text = Convert.ToString(reader[7]);
                //Label22.Text = Convert.ToString(reader[8]);
                //Label24.Text = Convert.ToString(reader[9]);
                //Label26.Text = Convert.ToString(reader[10]);
                //Label28.Text = Convert.ToString(reader[11]);
                //Label30.Text = Convert.ToString(reader[12]);
                //Label7.Text = Convert.ToString(reader[13]);

           
        }
        Panelconstruction.Visible = true;
        reader.Close();
       
            
        
      

    }

try to solve it plz....