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.

Drop.gif

 <%@ 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 DropDownList control in a page.

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