List Controls in ASP.NET - Part 2
Introduction
In Part – 1 article of
this series, we have discussed how to declare list items but still we have not
discussed how to bind it to databases. Let’s take a look on it.
Binding to Data Source
We can bind any of the List controls to a data source. The List
controls support both declarative databinding and programmatic databinding.
Declarative Databinding
The page given below contains a DropDownList, ListBox and BulletList controls
that is bound to the subject database table with declarative databinding.
<%@ Page Language="VB" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
<title></title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:DropDownList
id="ddlSubjects"
DataSourceID="SqlDataSource1"
DataTextField="SUBJECT"
DataValueField="ID"
Runat="server" />
<br />
<br />
<asp:ListBox
ID="lstSubject"
DataSourceID="SqlDataSource1"
DataTextField="SUBJECT"
DataValueField="ID"
runat="server"/>
<br />
<br />
<asp:BulletedList
ID="bltSubject"
DataSourceID="SqlDataSource1"
DataTextField="SUBJECT"
DataValueField="ID"
runat="server" />
<br />
<br />
<br />
<asp:SqlDataSource ID="SqlDataSource1" runat="server"
ConnectionString="<%$ ConnectionStrings:DatabaseConnectionString1 %>"
ProviderName="<%$ ConnectionStrings:DatabaseConnectionString1.ProviderName %>"
SelectCommand="SELECT [ID],
[SUBJECT] FROM [SUBJECT]"></asp:SqlDataSource>
</div>
</form>
</body>
</html>
Notice that the DropDownList, ListBox and BulletList control's DataSourceID property
points to the ID of the SqlDataSourcecontrol. When we open the
page the SqlDataSource control retrieves the records from the
subject database table.
Programmatic Databinding
As an alternative to declarative databinding, we can
programmatically bind any of the List controls to a data source. Take a look at
the example given below.
<%@ Page Language="VB" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
Public Class CartItem
Private _id As Integer
Public _description As String
Public ReadOnly Property Id() As Integer
Get
Return _id
End Get
End Property
Public ReadOnly Property Description() As String
Get
Return _description
End Get
End Property
Public Sub New(ByVal id As Integer, ByVal description As String)
_id
= id
_description
= description
End Sub
End Class
Private Sub Page_Load()
If Not IsPostBack Then
Dim shoppingCart As New List(Of CartItem)()
shoppingCart.Add(New CartItem(1, "Computer"))
shoppingCart.Add(New CartItem(2, "Television"))
shoppingCart.Add(New CartItem(3, "Boofer"))
lstShoppingCart.DataSource = shoppingCart
lstShoppingCart.DataBind()
End If
End Sub
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
<title></title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:ListBox
id="lstShoppingCart"
DataTextField="Description"
DataValueField="Id"
Runat="server" />
</div>
</form>
</body>
</html>
In above example, ListBox bound
to the collection in the Page_Load() method. Notice that
the DataTextField andDataValueField properties
of the ListBox control represent properties of the CartItem class. A List control's DataTextFieldand DataValueField properties
can refer to any public property of a class, but you cannot bind a List control
to a public field.
Note: Continue in Next Part.
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