Filling Dropdown box using Code-Behinds in C#

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Code-Behinds in C#

This simple example shows how to use code-behinds in ASP.NET. The following code fills a dropdown box selecting data from the pubs database. This is an example method of separating presentation from business logic.

Here is the code:

The webpage.

<%@ Page Language="C#" Debug="False" Inherits="myCodeBehind" src="2.cs"%>
<html>
<head><title>Fill dropdown with C# and Sql DataReader</title></head>
       <body>
           <asp:Dropdownlist id="atMyDropDownList" DataValueField = "au_lname" DataTextField = "au_id" runat="server" />
       </body>
</html>

The Code-behind page

using System;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.HtmlControls;
using System.Data;
using System.Data.SqlClient;
using System.Configuration;

public class myCodeBehind : System.Web.UI.Page
{
public DropDownList atMyDropDownList;

    private void Page_Load(object sender, System.EventArgs e)
    {
        string sqlText = "select * from authors";
        atMyDropDownList.DataSource = GetDr( sqlText );
        atMyDropDownList.DataBind();
    }
    private SqlDataReader GetDr( string sqlText)
    {
        SqlDataReader dr;
        SqlConnection sqlConn = new SqlConnection(ConnectionString());
        SqlCommand sqlCmd = new SqlCommand(sqlText,sqlConn);
        sqlCmd.Connection.Open();
        dr = sqlCmd.ExecuteReader(System.Data.CommandBehavior.CloseConnection);
        return dr;
    }
    private string ConnectionString()
        {
            return ConfigurationSettings.AppSettings["DSN_pubs"];
        }

    private void Page_Init( object Sender, System.EventArgs e)
    {

    }//end Page_Init

} //End Class

Web.Config holding application settings