ADO Net Database ASP.Net Tutorial

<%@ Page Language="C#" %>
<%@ import Namespace="System.Data" %>
<%@ import Namespace="System.Data.SqlClient" %>

    void Page_Load(object sender, EventArgs e) {
        if (!Page.IsPostBack)
        {
            string ConnectionString = ConfigurationSettings.AppSettings["MSDEConnectString"];
            SqlConnection myConnection = new SqlConnection(ConnectionString);
    
            try{
                string CommandTextPublisher = "SELECT PublisherID, PublisherName FROM Publisher";
                SqlCommand myCommandPublishers = new SqlCommand(CommandTextPublisher, myConnection);
    
                myConnection.Open();
    
                DropDownList1.DataSource = myCommandPublishers.ExecuteReader();
                DropDownList1.DataTextField = "PublisherName";
                DropDownList1.DataValueField = "PublisherID";
                DropDownList1.DataBind();
                DropDownList1.Items.Insert(0, new ListItem("-- All Publishers --", "0"));
            }
            catch (Exception ex){
                throw(ex);
            }
            finally{
                myConnection.Close();
            }
        }
    }
    
    void ApplyFilter_Click(Object sender, EventArgs e) {
        string ConnectionString = ConfigurationSettings.AppSettings["MSDEConnectString"];
        SqlConnection myConnection = new SqlConnection(ConnectionString);
    
        try{
            string CommandTextBooks = "SELECT Book.BookTitle, Publisher.PublisherName FROM Book INNER JOIN Publisher on Book.BookPublisherID = Publisher.PublisherID";
            string filterValue = DropDownList1.SelectedValue;
            if (filterValue != "0")
                CommandTextBooks += " WHERE Book.BookPublisherID = " + filterValue;
            CommandTextBooks+=" ORDER BY Book.BookTitle";
            SqlCommand myCommandBooks = new SqlCommand(CommandTextBooks, myConnection);
    
            myConnection.Open();
    
            DataGrid1.DataSource = myCommandBooks.ExecuteReader();
            DataGrid1.DataBind();
        }
        catch (Exception ex){
            throw(ex);
        }
        finally{
            myConnection.Close();
        }
    }





    
        
            Select a Publisher: 
            
              
            
        
        
            
            
        
    


File: Web.config