How to Use the ListBox Control in ASP.NET 2.0 - Dynamic binding to data at run time (Page 4 of 6 )
There are two ways you can populate the list with backend data. Well, not exactly two ways so much as two procedures using the same AccessDataSource Control.
Example 1: The Long hand
The first of these is a roundabout way of getting the result. It still uses the AccessDataSource control by starting off using its connectionString as shown in the following (litany?) snippet. This was how data was accessed using ADO.NET 1.0.
Imports System.Data.OleDb
Partial Class _Default
Inherits System.Web.UI.Page
Protected Sub Button1_Click(ByVal sender As Object, _
ByVal e As System.EventArgs) Handles Button1.Click
Dim ds As New AccessDataSource
ds = AccessDataSource1
Response.Write(ds.ConnectionString)
Dim mycon As New OleDbConnection
Dim conStr As String = ds.ConnectionString
mycon.ConnectionString = conStr
mycon.Open()
Response.Write("<h2>" & mycon.State & "</h2>")
Dim myCmd As New OleDbCommand
myCmd.Connection = mycon
myCmd.CommandType = Data.CommandType.Text
myCmd.CommandText = ds.SelectCommand.ToString
Try
Dim dr As OleDbDataReader = myCmd.ExecuteReader
Response.Write(dr.HasRows)
'Dim str As String = ""
While dr.Read
ListBox1.Items.Add(dr.Item("CustomerID") & _
"," & dr.Item("CompanyName") & "," & _
dr.Item("LastName") & "," & _
dr.Item("City") & "," _
& dr.Item("HomePhone"))
'Response.Write(str)
End While
dr.Close()
Catch ex As System.Data.OleDb.OleDbException
Response.Write(ex.Message)
End Try
mycon.Close()
End Sub
End Class
You may recall that this code is similar to what was formerly used in the VS2003 and described in a previously referenced article. The Design pane of this page (Default.aspx) is shown in the next picture followed by the source code listing of the page. In the source code make sure that the SelectCommand is all in one line. It should work as is except that the VS2005 IDE editor may emit some errors (it will work in spite of the emitted HTML error).
<%@ Page Language="VB" AutoEventWireup="false" CodeFile="Default.aspx.vb" Inherits="_Default" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>Longwinded</title>
</head>
<body>
<form id="form1" runat="server">
<div id="DIV1" runat="server">
<asp:ListBox ID="ListBox1" runat="server"
AppendDataBoundItems="True" AutoPostBack="false"
Height="172px" Width="650px" >
</asp:ListBox><asp:AccessDataSource
ID="AccessDataSource1" runat="server"
DataFile="~/App_Data/nwind.mdb"
SelectCommand="SELECT Customers.CustomerID,
Customers.CompanyName, Customers.ContactName,
Employees.LastName, Employees.City, Employees.HomePhone,
Orders.OrderDate
FROM ((Customers INNER JOIN Orders ON
Customers.CustomerID = Orders.CustomerID)
INNER JOIN Employees ON
Orders.EmployeeID = Employees.EmployeeID)
WHERE (Orders.OrderDate > #5/1/1998#)">
</asp:AccessDataSource>
<asp:Button ID="Button1" runat="server"
Text="Button" /></div>
</form>
</body>
</html>
Example 2: Using DataSource directly
The code behind shown for this CodeBound.aspx is simple and effortless thanks to the ADO.NET 2.0 DataSource controls. Some of the AccessDataSource controls' properties are used. The source code listing is also simpler as shown. The design pane of this example is exactly the same as in the previous example (Default.aspx). For this example you add the ListBox to the design pane and attach the datasource; you can get drop-down hints for writing the code.
First, the code behind the click event of the button.
Imports System.Data.OleDb
Partial Class CodeBound
Inherits System.Web.UI.Page
Protected Sub Button1_Click(ByVal sender As Object, _
ByVal e As System.EventArgs) Handles Button1.Click
Dim ds As New AccessDataSource
ds = AccessDataSource1
Dim sqlstr As String = "Select * from Customers"
ds.SelectCommand = sqlstr
ListBox1.DataSource = ds
ListBox1.DataValueField = "CustomerID"
ListBox1.DataTextField = "CompanyName"
ListBox1.DataBind()
End Sub
End Class
The source code listing of CodeBound.aspx is much simpler than the previous case as shown below. Less code is the key word here.
<%@ Page Language="VB" AutoEventWireup="false"
CodeFile="CodeBound.aspx.vb" Inherits="CodeBound" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>Code Bound</title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:ListBox ID="ListBox1" runat="server" Height="177px"
Width="333px">
</asp:ListBox><asp:AccessDataSource
ID="AccessDataSource1" runat="server"
DataFile="~/App_Data/nwind.mdb"
SelectCommand="SELECT [CustomerID], [CompanyName],
[City], [Phone] FROM [Customers]">
</asp:AccessDataSource>
<br />
<br />
<asp:Button ID="Button1" runat="server"
Text="Button" /></div>
</form>
</body>
</html>
This page gets rendered as shown in the next picture when the button is clicked.
Next: Databound ListBox Example >>
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