Ch 6 - User-Selected theme not working

jennyWren · December 15th, 2009, 06:30 PM

Hi

I've read the posts here and tried all ways - but this swap just isn't working. Only one of the backgrounds is showing - ie the one whose name is included in the web.config page. The page is re-loading each time, but I'm only getting the one background.

I had to change the ID of the dropdown from "1stPreferredTheme" to "FirstPreferredTheme" as the program didn't seem to like it - ie line underneath in the VB page code.

I'm not getting an error.

Any ideas?

Thanks

Imar · December 16th, 2009, 05:20 AM

Hi there,

Did you write code in the Master Page and in the BasePage? And is your page inheriting that BasePage?

BTW: it's lst as in list, not 1st as in first. Check out the errata for that (and other) changes / errors / explanations in the book,

If that doesn't help, can you post the code for the relevant code files (master page, page and BasePage)?

Cheers,

Imar

jennyWren · December 16th, 2009, 04:47 PM

Oops - of course btn, lst, txt (I forgot). The times new roman style of type in the book made it look like 1st - but, I should have known.

Anyway I seem to be going around in circles so here is the code -

BasePage.vb

Code:

Public Class BasePage
    Inherits System.Web.UI.Page

    Private Sub Page_PreInit(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.PreInit
        Dim preferredTheme As HttpCookie = Request.Cookies.Get("PreferredTheme")
        If preferredTheme IsNot Nothing Then
            Page.Theme = preferredTheme.Value
        End If
    End Sub


    Private Sub Page_PreRender(ByVal sender As Object, ByVal e As System.EventArgs) _
    Handles Me.PreRender
        If Me.Title = "" Then
            Throw New Exception("Page title cannot be blank.")
        End If
    End Sub
End Class

Web_config

<pages theme ="Monochrome"> (amongst other default code)

MasterPage.master.vb

Code:

Partial Class MasterPage
    Inherits System.Web.UI.MasterPage

    Protected Sub lstPreferredTheme_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles lstPreferredTheme.SelectedIndexChanged
        Dim preferredTheme As HttpCookie = New HttpCookie("PreferredTheme")
        preferredTheme.Expires = DateTime.Now.AddMonths(3)
        preferredTheme.Value = lstPreferredTheme.SelectedValue
        Response.Cookies.Add(preferredTheme)
        Response.Redirect(Request.Url.ToString())
    End Sub

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        If Not Page.IsPostBack Then
            Dim selectedTheme As String = Page.Theme
            Dim preferredTheme As HttpCookie = Request.Cookies.Get("PreferredTheme")
            If preferredTheme IsNot Nothing Then
                selectedTheme = preferredTheme.Value
            End If
            If lstPreferredTheme.Items.FindByValue(selectedTheme) IsNot Nothing Then
                lstPreferredTheme.Items.FindByValue(selectedTheme).Selected = True
            End If
        End If
    End Sub
End Class

MasterPage.master

Code:

<%@ Master Language="VB" CodeFile="MasterPage.master.vb" Inherits="MasterPage" %>

<!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></title>
     
</head>
<body>
    <form id="form1" runat="server">
    <div id="PageWrapper">
    <div id="Header"><a class="HeaderLink" href="~/" runat="server">Header Goes Here</a></div>
    <div id="MenuWrapper">Menu Goes here</div>
    <div id="MainContent">

        <asp:ContentPlaceHolder id="cpMainContent" runat="server">
        </asp:ContentPlaceHolder>
        </div>
        
        <div id="Sidebar">Select a theme 
            <asp:DropDownList ID="lstPreferredTheme" runat="server" AutoPostBack="True" OnSelectedIndexChanged="lstPreferredTheme_SelectedIndexChanged">
                <asp:ListItem>Monochrome</asp:ListItem>
                <asp:ListItem>DarkGrey</asp:ListItem>
            </asp:DropDownList>
        </div>
        <div id="Footer">Footer Goes Here</div>
    </div>
    </form>
    
</body>
</html>

Thanks

Imar · December 16th, 2009, 06:41 PM

Hi jenny,

That all looks pretty much like it should except for one thing:

<asp:DropDownList ID="lstPreferredTheme" runat="server" AutoPostBack="True" OnSelectedIndexChanged="lstPreferredTheme_Selected IndexChanged">

The handler setup for OnSelectedIndexChanged is not needed (as the Code Behind already defines this using the Handles keyword) and would cause the code to trigger twice. However, I don't think that's causing the problem.

Can it be the Web Form you're trying this out on? Maybe that page does not inherit BasePage so PreInit which applies the theme is never called? Can you post the code for that page too?

Cheers,

Imar

jennyWren · December 17th, 2009, 08:17 AM

This is default.aspx

Code:

<%@ Page Title="" Language="VB" MasterPageFile="~/MasterPages/MasterPage.master" AutoEventWireup="true" CodeFile="Default.aspx.vb" Inherits="_Default" %>

<asp:Content ID="Content1" ContentPlaceHolderID="cpMainContent" Runat="Server">
    <h1>
    Hi there visitor and welcome to Planet Wrox</h1>
<p class="Introduction">
    We're glad you're paying a visit to <a href="http://www.PlanetWrox.com">
    www.PlanetWrox.com</a> the coolest music community on the Internet.</p>
<p class="Introduction">
    Feel free to have a <a href="Default.aspx">look around</a>, as there are lots of 
    interesting <b>reviews and concert pictures</b> to be found here.</p>
<p class="Introduction">
    You can <a href="Login.aspx">log in</a> here.</p>
</asp:Content>

I have just noticed that I don't seem to have much on this page anymore. No reference to HTML etc.

jennyWren · December 17th, 2009, 08:26 AM

I remember now - I got rid of it when making the master page.

Imar · December 17th, 2009, 08:36 AM

And can you post the Code Behind for this page?

Imar

jennyWren · December 17th, 2009, 08:55 AM

Finally works -

Within the Default.aspx.vb page I compared it to your example and found that the bit stating "Inherits BasePage" was assigned to

Code:

 Partial Class _Default
    Inherits System.Web.UI.Page
End Class

which was probably my default. I can't see it stated in the book.

Its a great example anyway. Theres always something small that causes problems - Thanks.

Imar · December 17th, 2009, 09:34 AM

Yeah, that's what I though. Normally, this is how the inheritance change looks:

Code:

 
YourPage
  System.Web.UI.Page

When you inherit BasePage, this changes to:

Code:

 
YourPage
  BasePage
    System.Web.UI.Page

That is, BasePage can do anyhting System.Web.UI.Page can. And YourPage can do anything BaseBase can.

If you leave out the BasePage, the behavior defined in that class never runs, and thus the theme is never applied.

Hope this clarifies things.

Cheers,

Imar

StamPita · December 17th, 2009, 12:39 PM

Hello Imar,

I have the same problem as well (but in C#). Of coursed i followed every step in the book, read your comments above and also tryed to match every file in the Source folder to the Site folder (master, master.cs, default, default.cs, web.config, and BasePage). I also checked for Capital letters in the .cs files... but I have no idea what's wrong. can you please help me with that?

Thanks a lot!