<%@ Page Language="C#" AutoEventWireup="true" %> <%@ Register Src="Control.ascx" TagName="VaryByControl" TagPrefix="uc1" %> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" > <head runat="server"> <title>Untitled Page</title> </head> <body> <form id="form1" runat="server"> <div> <uc1:VaryByControl ID="VaryByControl1" runat="server" /> </div> </form> </body> </html> File: Control.ascx <%@ Control Language="C#" AutoEventWireup="true" CodeFile="Control.ascx.cs" Inherits="VaryByControl" %> <%@ OutputCache Duration="30" VaryByControl="lstMode" %> <asp:DropDownList id="lstMode" runat="server" Width="187px"> <asp:ListItem>Large</asp:ListItem> <asp:ListItem>Small</asp:ListItem> <asp:ListItem>Medium</asp:ListItem> </asp:DropDownList> <br /> Control generated at:<br /> <asp:label id="TimeMsg" runat="server" /> File: Control.ascx.cs using System; using System.Data; using System.Configuration; using System.Collections; using System.Web; using System.Web.Security; using System.Web.UI; using System.Web.UI.WebControls; using System.Web.UI.WebControls.WebParts; using System.Web.UI.HtmlControls; public partial class VaryByControl : System.Web.UI.UserControl { protected void Page_Load(object sender, EventArgs e) { switch (lstMode.SelectedIndex) { case 0: TimeMsg.Font.Size = FontUnit.Large; break; case 1: TimeMsg.Font.Size = FontUnit.Small; break; case 2: TimeMsg.Font.Size = FontUnit.Medium; break; } TimeMsg.Text = DateTime.Now.ToString("F"); } }