Drop-Down List Control in ASP.NET
Introduction & Demonstration
The DropDownList control
enables us to display a list of options while requiring a minimum of screen
real estate. A user can select only one option at a time when using this
control.
The page given below
illustrates how we can use the DropDownList control
to display all the product titles from the PRO_LIST database table.
<%@ 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">
<script runat="server">
Protected Sub btnSubmit_Click(ByVal sender As Object, ByVal e As EventArgs)
lblProducts.Text
= ddlProducts.SelectedItem.Text
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:DropDownList
id="ddlProducts"
DataSourceID="SqlDataSource1"
DataTextField="TITLE"
DataValueField="ID"
Runat="server" />
<asp:Button
id="btnSubmit"
Text="Submit"
OnClick="btnSubmit_Click"
Runat="server" />
<hr />
<asp:Label
id="lblProducts"
Runat="server" />
<asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:DatabaseConnectionString1 %>"
ProviderName="<%$
ConnectionStrings:DatabaseConnectionString1.ProviderName %>"
SelectCommand="SELECT [ID],
[TITLE] FROM [PRO_LIST]"></asp:SqlDataSource>
</div>
</form>
</body>
</html>
The DropDownList control renders an HTML <select> tag.
One problem with the HTML <select> tag is that it has
an infinite z index. In other words, we can't place other objects, such as an
absolutely positioned <div> tag, in front of a DropDownListcontrol
in a page.
Note: Continue in Next Part.
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