Thank you for your reply. Here is both the MasterDemo.Master and MasterDemo.Master.cs
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MasterDemo.Master
******************
<%@ Master Language="C#" AutoEventWireup="true" CodeFile="MasterDemo.master.cs" Inherits="MasterPages_MasterDemo" %>
<!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>Untitled Page</title>
<asp:ContentPlaceHolder id="head" runat="server">
</asp:ContentPlaceHolder>
</head>
<body>
<form id="form1" runat="server">
<div id="PageWrapper">
<div id="Header">Header<a class="HeaderLink" href="~/" runat="server"><asp:SiteMapDataSource
ID="SiteMapDataSource1" runat="server" ShowStartingNode="False" />
</a></div>
<div id="MenuWrapper">
<asp:Menu ID="Menu1" runat="server" CssClass="MainMenu"
DataSourceID="SiteMapDataSource1" Orientation="Horizontal"
StaticEnableDefaultPopOutImage="False">
<StaticSelectedStyle CssClass="StaticSelectedStyle" />
<StaticMenuItemStyle CssClass="StaticMenuItemStyle" ForeColor="Black" />
<DynamicHoverStyle CssClass="DynamicHoverStyle" />
<DynamicMenuItemStyle CssClass="DynamicMenuItemStyle" />
<StaticHoverStyle CssClass="StaticHoverStyle" />
</asp:Menu>
</div>
<div id="MainContent">
<asp:ContentPlaceHolder ID="cpMainContent" runat="server">
<asp:TreeView ID="TreeView1" runat="server" DataSourceID="SiteMapDataSource1"
ShowExpandCollapse="False">
</asp:TreeView>
</asp:ContentPlaceHolder>
</div>
<div id="Sidebar">
<asp:DropDownList ID="lstPreferredTheme" runat="server" AutoPostBack="True"
onselectedindexchanged="lstPreferredTheme_Selected IndexChanged">
<asp:ListItem Value="Monochrome"></asp:ListItem>
<asp:ListItem>DarkGrey</asp:ListItem>
</asp:DropDownList>
</div>
<div id="Footer">Footer Goes Here</div>
</div>
</form>
</body>
</html>
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MasterDemo.Master.cs
********************
using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Linq;
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;
using System.Xml.Linq;
public partial class MasterPages_MasterDemo : System.Web.UI.MasterPage
{
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
string selectedTheme = Page.Theme;
HttpCookie preferredTheme = Request.Cookies.Get("PreferredTheme");
if (preferredTheme != null)
{
selectedTheme = preferredTheme.Value;
}
if (lstPreferredTheme.Items.FindByValue(selectedTheme ) != null)
{
lstPreferredTheme.Items.FindByValue(selectedTheme) .Selected = true;
}
}
switch (Page.Theme.ToLower())
{
case "darkgrey":
Menu1.Visible = false;
TreeView1.Visible = true;
break;
default:
Menu1.Visible = true;
TreeView1.Visible = false;
break;
}
}
protected void lstPreferredTheme_SelectedIndexChanged(object sender, EventArgs e)
{
HttpCookie preferredTheme = new HttpCookie("preferredTheme");
preferredTheme.Expires = DateTime.Now.AddMonths(3);
preferredTheme.Value = lstPreferredTheme.SelectedValue;
Response.Cookies.Add(preferredTheme);
Response.Redirect(Request.Url.ToString());
}
}
Chapter 7 Object reference error in master.cs
Linear Mode
