Skins not changing from dropdown box on homepage

Question

User1673739617 posted

 Hi,

I'm using the Personal Starter Kit with ASP.Net 2.0.
I am unable to change the Skin colour from the drop-down box on my homepage:
http://www.birchdalegardens.com/

as you can see its not generating any error, but at the same time it's not changing the Skin.

I have the APP_Themes folder with all the required files in it, and have the MASTER Pages folder as well, but still no joy...

[b]Do I need to add something to my web.config (see below)[/b]

can anyone suggest how I can fix it?


<?xml version="1.0"?>
<configuration xmlns="http://schemas.microsoft.com/.NetConfiguration/v2.0">
    <connectionStrings>
        <!-- Connection for SQL 2005 Express -->
        <remove name="Personal"/>
        <add name="Personal" connectionString="Data Source=.....;uid=...;password='....';Initial catalog=....." providerName="System.Data.SqlClient"/>
        <!-- Connection for SQL Server 2005 -->
        <!--<add name="Personal" connectionString="Server=(Local);Integrated Security=True;database=Personal" providerName="System.Data.SqlClient"/>-->
        <remove name="LocalSqlServer"/>
        <!-- Connection for SQL 2005 Express -->
        <add name="LocalSqlServer" connectionString="Data Source=......;uid=.....;password='.....';Initial catalog=......." providerName="System.Data.SqlClient"/>
        <!-- Connection for SQL Server 2005 -->
        <!--<add name="LocalSqlServer" connectionString="Server=(Local);Integrated Security=True;database=Personal" providerName="System.Data.SqlClient"/>-->
    </connectionStrings>
    <system.web>
    <pages>
            <namespaces>
                <clear/>
                <add namespace="System"/>
                <add namespace="System.Collections"/>
                <add namespace="System.Collections.Specialized"/>
                <add namespace="System.Configuration"/>
                <add namespace="System.Text"/>
                <add namespace="System.Text.RegularExpressions"/>
                <add namespace="System.Web"/>
                <add namespace="System.Web.Caching"/>
                <add namespace="System.Web.SessionState"/>
                <add namespace="System.Web.Security"/>
                <add namespace="System.Web.Profile"/>
                <add namespace="System.Web.UI"/>
                <add namespace="System.Web.UI.WebControls"/>
                <add namespace="System.Web.UI.WebControls.WebParts"/>
                <add namespace="System.Web.UI.HtmlControls"/>
                <add namespace="System.Data"/>
                <add namespace="System.Data.Sql"/>
                <add namespace="System.Data.SqlClient"/>
            </namespaces>
        </pages>
        <httpHandlers>
            <add type="PeterKellner.Utils.CaptchaTypeHandler" verb="GET" path="CaptchaType.ashx"/>
        </httpHandlers>

        <customErrors mode="Off"/>
        <compilation debug="true">
            <assemblies>
                <add assembly="System.Design, Version=2.0.0.0, Culture=neutral, PublicKeyToken=B03F5F7F11D50A3A"/></assemblies></compilation>
        <authentication mode="Forms">
            <forms loginUrl="Login.aspx" protection="Validation" timeout="50000" />
        </authentication>
        <authorization>
            <allow users="*"/>
        </authorization>
        <globalization requestEncoding="utf-8" responseEncoding="utf-8"/>
        <membership>
   <providers>
    <add connectionStringName="LocalSqlServer" enablePasswordRetrieval="false"
     enablePasswordReset="true" requiresQuestionAndAnswer="true" applicationName="/"
     requiresUniqueEmail="true" minRequiredPasswordLength="6" minRequiredNonalphanumericCharacters="0"
     passwordStrengthRegularExpression="" passwordFormat="Hashed"
     passwordAttemptWindow="10" name="DefaultMembershipProvider" type="System.Web.Security.SqlMembershipProvider, System.Web, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" />
    <add connectionStringName="LocalSqlServer" enablePasswordRetrieval="false"
     enablePasswordReset="true" requiresQuestionAndAnswer="false"
     applicationName="/" requiresUniqueEmail="true" minRequiredPasswordLength="6"
     minRequiredNonalphanumericCharacters="0" passwordStrengthRegularExpression=""
     passwordFormat="Hashed" passwordAttemptWindow="10" name="AdminMembershipProvider"
     type="System.Web.Security.SqlMembershipProvider, System.Web, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" />
   </providers>
  </membership>
        <profile>
            <properties>
                <add name="FirstName"/>
                <add name="LastName"/>
                <add name="Website"/>
                <add name="PasswordAnswer"/>
            </properties>
        </profile>
        <roleManager enabled="true" />
        <siteMap defaultProvider="XmlSiteMapProvider" enabled="true">
            <providers>
                <add name="XmlSiteMapProvider" description="SiteMap provider which reads in .sitemap XML files." type="System.Web.XmlSiteMapProvider, System.Web, Version=2.0.3600.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" siteMapFile="web.sitemap" securityTrimmingEnabled="true"/>
            </providers>
        </siteMap>
    </system.web>
    <system.net>
        <mailSettings>
            <smtp from="[e-mail]">
                <network host="smtp.yourdomain.net" userName="yourusername" password="yourpassword" />
            </smtp>
        </mailSettings>
    </system.net>
    <location path="~/Albums/4/61.jpg">
        <system.web>
            <authorization>
                <allow roles="Family"/>
                <deny users="*"/>
            </authorization>
        </system.web>
    </location>
    <!--<location path="Downloads">
        <system.web>
          <authorization>
            <allow roles="Administrators,Registered Users"/>
            <deny users="*"/>
          </authorization>
        </system.web>
    </location>-->
  <location path="App_Themes">
    <system.web>
      <authorization>
        <allow users="*"/>
      </authorization>
    </system.web>
  </location>
 
    <location path="Admin">
        <system.web>
            <authorization>
                <allow roles="Administrators"/>
                <deny users="*"/>
            </authorization>
        </system.web>
    </location>
    <appSettings>
        <!-- The Album Path needs to be in the form of "~/FolderName"
             When the application creates an album to store photos in, it will create the album inside the folder
             specified here. -->
        <add key="AlbumsFolder" value="~/Albums" />

        <!-- This key specifies the folder to use for Uploads. At this time there is at least one stored procedure that
             still references the upload folder statically. Once that is changed you would be able to specify any folder
             here that the application should use for working with Uploaded photos that have not been imported to an album.-->
        <add key="UploadFolder" value="~/Upload" />

        <!-- This key defines what role a new user will be assigned to by default. If set to blank, the user will be
             created but not assigned to any roles. The user would then need to be assigned to a role by the administrator
             before they would have an special access to the website.-->
        <add key="DefaultRoleForNewUser" value="Registered Users"/>

        <!-- This key defines the theme that will be used on the admin pages. I created this setting because it will
             reduce the time it takes to create a new theme if you don't have to create all new buttons and css to go with
             administration pages. I found it easier just to have the admin sections use the White theme. If left blank the
             admin pages will use whatever theme is selected for the site. -->
        <add key="AdminTheme" value="White"/>

        <!-- This key defines the user account to be notified for all site notification. Guestbook entry, blog comments, new user, etc. -->
        <add key="NotifyAccount" value="Admin"/>

        <!-- This key defines the email address to send errors to. It is defined here in case the error is generated
            as a result of a database connection in which we would not be able to retrieve the admin email -->
        <add key="AdminEmail" value="[e-mail]"/>
        
    </appSettings>
</configuration>

Answer 1

User986106991 posted

Hello Ricky,

You can change the theme of your web page at run time by adding following code in Page_PreInit event:

Page.Theme = ddlThemes.Text;  //Make sure that you re-set theme only in PreInit event.  

Also, i visited your web-site, and noticed that value in Skin DropDownList is not getting re-set,
whatever we select, it will again show "default" as selected after post-back.
Please re-check the code you have written on Page_Load of your content as well as master page.

Post your code, if above does not solve your problem.

Good luck!

Answer 2

User1673739617 posted

Hi, On what page would the pre_init event above go? Can you send me this block of code, to change the theme at run-time?

Still can't get it to work. I attach 2 lots of code below 1) page_load event in default.aspx and 2) master pages default theme code

 

 

here is my page_load event code in default.aspx.vb

 

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        If Page.IsPostBack = False Then
            Dim objSiteContent As SiteContent
            Dim myList As Generic.List(Of SiteContent) = SiteContentManager.GetSiteContent()
            Dim objSettings As SiteSettings = SiteSettingsManager.GetSiteSettings()

            For Each objSiteContent In myList
                With objSiteContent
                    Select Case .ContentName.ToUpper
                        Case "WELCOME"
                            If .IsVisible = 1 Then
                                lblWelcomeText.Text = .ContentText
                                lblWelcomeTitle.Text = .ContentTitle
                            End If

                        Case "WHATSNEW"
                            If .IsVisible = 1 Then
                                lblWhatsNewTitle.Text = .ContentTitle
                                lblWhatsNewText.Text = .ContentText
                            End If

                        Case "LATESTNEWS"
                            If .IsVisible = 1 Then
                                lblLatestNewsTitle.Text = .ContentTitle
                                lblLatestNewsText.Text = .ContentText
                            End If

                    End Select
                End With
            Next

            Session("Theme") = objSettings.ThemeName
            If CBool(Session.Item("EnableUserThemes")) = True Then
                'Portal Specific Reference

                mstrTheme = objSettings.ThemeName

                drpThemes.DataSource = Globals.GetThemesList()
                drpThemes.DataBind()
                drpThemes.SelectedValue = mstrTheme
                drpThemes.Visible = True
                lblSelectSkin.Visible = True
            Else
                drpThemes.Visible = False
                lblSelectSkin.Visible = False
            End If


        Else
            mstrTheme = CStr(Session("Theme"))
        End If

    End Sub

    Protected Sub Page_PreRender(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.PreRender
        Dim blnAdminAuth As Boolean = Roles.IsUserInRole("Administrators")
        ibtnEditWelcome.Visible = blnAdminAuth
        ibtnEditWhatsNew.Visible = blnAdminAuth
        ibtnEditLatestNews.Visible = blnAdminAuth
        ibtnBlogEntryAdd.Visible = blnAdminAuth

    End Sub

    Protected Sub drpThemes_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles drpThemes.SelectedIndexChanged
        SiteSettingsManager.UpdateSiteSettings(1, drpThemes.SelectedItem.Value)

        Response.Redirect("Default.aspx")
    End Sub

    Public Sub Randomize(ByVal sender As Object, ByVal e As EventArgs)
        Dim r As Random = New Random
        FormView1.PageIndex = r.Next(FormView1.PageCount)
    End Sub
End Class

 

 

here is my code for my master pages default theme

 

Partial Class Default_Master
    Inherits System.Web.UI.MasterPage

    Protected Sub Page_PreRender(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.PreRender
        If Page.IsPostBack = False Then
            Page.Title = Session.Item("SitePageTitle")
            lblSiteName.Text = Session.Item("SiteName")
            lblSiteSlogan.Text = Session.Item("SiteSlogan")
            lblCopyrightCredits.Text = Session.Item("CopyrightCredits")
        End If

        Dim metaTag As New HtmlMeta
        Dim HeadTag As HtmlHead = CType(Page.Header, HtmlHead)

        metaTag.Attributes.Add("name", "description")
        metaTag.Attributes.Add("content", CStr(Session.Item("MetaDescription")))
        HeadTag.Controls.Add(metaTag)

        metaTag = New HtmlMeta
        metaTag.Attributes.Add("name", "keywords")
        metaTag.Attributes.Add("content", CStr(Session.Item("MetaKeywords")))
        HeadTag.Controls.Add(metaTag)
    End Sub

    Protected Sub menua_MenuItemDataBound(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.MenuEventArgs) Handles menua.MenuItemDataBound
        ' Check for the Register menu item
        If e.Item.Text = "Register" Then
            ' Set the visibility of the Register menu item based on site settings from db
            If (CBool(Session.Item("EnableRegistration")) = False) Or (Context.User.Identity.IsAuthenticated = True) Then
                e.Item.Parent.ChildItems.Remove(e.Item)
            End If
        End If
    End Sub

    Protected Sub menub_MenuItemDataBound(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.MenuEventArgs) Handles menub.MenuItemDataBound
        ' Check for the Register menu item
        If e.Item.Text = "Register" Then
            ' Set the visibility of the Register menu item based on site settings from db
            If CBool(Session.Item("EnableRegistration")) = False Then
                e.Item.Parent.ChildItems.Remove(e.Item)
            End If
        End If
    End Sub

    Protected Sub menua_MenuItemClick(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.MenuEventArgs) Handles menua.MenuItemClick

    End Sub
End Class

Answer 3

User986106991 posted

one question:

Have you added Themes dropdownlist on your content page or master page?
I feel it should be added on master page, if you have not done that.

Answer 4

User1673739617 posted

On what page should i be adding the themes dropdown list?

there is no master page(s) in the root of my website, all master pages are saved in a folder called "master pages"...

 

here is the code for my default.master page  in the "master pages" folder:

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

<!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" xml:lang="en" >
<head runat="server">
    <title></title>
    <script type="text/javascript" language="javascript" src="../Lytebox/lytebox.js"></script>
    <link rel="stylesheet" href="../Lytebox/lytebox.css" type="text/css" media="screen" />
    <link rel="alternate" type="application/rss+xml" title="Jeremy Wadsworth's Blog" href="http://www.jeremywadsworth.com/RSSFeed.aspx" />
</head>
<body>

    <form id="form1" runat="server">
        <div class="header">
            <table id="SiteNameContainer" align="left" cellpadding="5" cellspacing="0" border="0">
                <tr>
                    <td valign="top" align="left">
                        &nbsp;&nbsp;<asp:Label ID="lblSiteName" CssClass="SiteName" runat="server" /></td>
                </tr>
                <tr>
                    <td valign="top" align="left">
                        &nbsp;&nbsp;&nbsp;&nbsp;<asp:Label ID="lblSiteSlogan" CssClass="SiteSlogan" runat="server" /></td>
                </tr>
            </table>
            <asp:menu id="menua" runat="server"
                datasourceid="SiteMapDataSource1"
                cssclass="menua"
                orientation="Horizontal"
                maximumdynamicdisplaylevels="0"
                skiplinktext=""
                staticdisplaylevels="2" />
            <div class="nav">
                <%--<asp:SiteMapPath id="SiteMapPath1" runat="Server" PathSeparator=" > " RenderCurrentNodeAsLink="true" />
                &nbsp; | &nbsp;--%>
                <asp:loginview id="LoginArea" runat="server">
                    <LoggedInTemplate>
                        <asp:loginname id="LoginName1" runat="server" formatstring="Logged in as {0}!  |  " /><asp:HyperLink ID="HyperLink1" runat="server" Text="My Profile" NavigateUrl="~/MyProfile.aspx" /> |
                    </LoggedInTemplate>
                </asp:loginview>
                <asp:LoginStatus ID="LoginStatus1" Runat="server" LogoutPageUrl="~/Default.aspx" LogoutAction="Redirect" />
            </div>
        </div>

        <asp:contentplaceholder id="Main" runat="server" />

        <div class="footerbg">
            <div class="footer">
                <asp:menu id="menub" runat="server"
                    datasourceid="SiteMapDataSource1"
                    cssclass="menub"
                    orientation="Horizontal"
                    maximumdynamicdisplaylevels="0"
                    skiplinktext=""
                    staticdisplaylevels="2" />
                <asp:Label ID="lblCopyrightCredits" runat="server" />
            </div>
        </div>

        <asp:sitemapdatasource id="SiteMapDataSource1" runat="server" startingnodeoffset="0" />
   
    </form>
</body>
</html>

 

thanks

 

 

 

 

Answer 5

User986106991 posted

Add Themes dropdownlist to the master page - that you are using as a template for all other web-pages.
Is there any reason to have multiple master pages in your web-site?

I am working on some code and will soon post code for dynamic - application level theme changes.

Good Luck!

 

Answer 6

User1673739617 posted

Sorry, i'm fairly new to asp.net. The personal starter kit, im using is from a download on the jeremy wadsworth website, in this example there are multiplemaster pages within a master pages folder...

 

I look forward to seeing and testing your code...

 

 

 

Answer 7

User595806616 posted

The following code should fix the problem. This code replace everything in the Global.asax file.

 

 

1    <%@ Application Language="VB" %>
2    
3    <script runat="server">
4    
5    	Sub Application_Start(ByVal sender As [Object], ByVal e As EventArgs)
6    		AddHandler SiteMap.SiteMapResolve, AddressOf Me.AppendQueryString
7    		If (Roles.RoleExists("Administrators") = False) Then
8    			Roles.CreateRole("Administrators")
9    		End If
10   		If (Roles.RoleExists("Friends") = False) Then
11   			Roles.CreateRole("Friends")
12   		End If
13   		
14   		' Set our user count to 0 when we start the server 
15   		Application("ActiveUsers") = 0
16   	End Sub
17   	
18   	Sub Session_OnStart(ByVal sender As [Object], ByVal e As EventArgs)
19   		Session.Timeout = 10
20   		Session("Start") = Now
21   		Application.Lock()
22   		Application("ActiveUsers") = CInt(Application("ActiveUsers")) + 1
23   		Application.UnLock()
24   		
25           'SiteSettingsManager.UpdateSiteSettings(1, "Default")
26   	End Sub
27   	
28   	Sub Session_OnEnd(ByVal sender As [Object], ByVal e As EventArgs)
29   		Application.Lock()
30   		Application("ActiveUsers") = CInt(Application("ActiveUsers")) - 1
31   		Application.UnLock()
32   	End Sub
33   
34   	Function AppendQueryString(ByVal o As [Object], ByVal e As SiteMapResolveEventArgs) As SiteMapNode
35   		If (Not (SiteMap.CurrentNode) Is Nothing) Then
36   			Dim temp As SiteMapNode
37   			temp = SiteMap.CurrentNode.Clone(True)
38   			Dim u As Uri = New Uri(e.Context.Request.Url.ToString)
39   			temp.Url = (temp.Url + u.Query)
40   			If (Not (temp.ParentNode) Is Nothing) Then
41   				temp.ParentNode.Url = (temp.ParentNode.Url + u.Query)
42   			End If
43   			Return temp
44   		Else
45   			Return Nothing
46   		End If
47   	End Function
48   
49   </script>

 

Answer 8

User986106991 posted

Hello Ricky,

I hope that last post by Jeremy Wadsworth would have solved your problem.
But in case you are still stuck, then I am here with some sample code [:)]

I will start with few quick notes about Themes and Skins:
   - Themes allows us to change the appearance of web-pages and
     different themes in a web-site helps user to select a theme of his own personal choice.
   - During development, we can apply themes at three different levels:
         1. Web-site level (setting required in web.config file)
         2. Page Level (setting required in <%@ Page … %> directive)
         3. Control Level (required to set SkinId property of the control)
     For further reading about this, you can follow this link:
     http://www.code-magazin.de/article.aspx?quickid=0709061&page=5

Now, my post perhaps will not address your sample application problem
but for sure, it will help you to understand how to : Change Web-Site Theme at run-time in ASP.Net 2.0

Before we jump onto steps, note that in my sample code,
Themes DropdownList control is in .master page that I am using as a template for my web-pages.

STEP# 1:
Create a class, BasePage.cs in App_Code folder and inherit it from System.Web.UI.Page
Following is the code for this class:

namespace MyWebSite
{

    /// <summary>
    /// This class will serve as base class for all the web pages in my web-site.
    /// </summary>

    public class BasePage : System.Web.UI.Page
    {
        public BasePage()
        { 

        } 

        protected void Page_PreInit(Object sender, EventArgs e)
        {
            if (Session["Theme"] != null)
            {
                //Create object of DropDownList control available in Master Page, 
                //you can access the Master page by using Page.Master
                DropDownList ddlThemes = (DropDownList)Page.Master.FindControl("ddlThemes");    
                ddlThemes.SelectedValue = Session["Theme"].ToString();
                //Re-set Page Theme with Session Variable
                this.Theme = Session["Theme"].ToString();
            }
            else
            {
                //Create Session variable, it should contain the theme name, that you want should be selected by default
                //Here, i wanted my theme "Caribbean Sun" to show by default
                Session["Theme"] = "Caribbean Sun";     
                this.Theme = "Caribbean Sun"; 
            }
        }
    }
}

All the content web-pages in web-site will inherit from this class as shown below:<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /><o:p></o:p>

public partial class SayHello : MyWebSite.BasePage
{
  //class body
}

The reason I have created BasePage class is to avoid code duplication and take advantage of inheritance.
If I don’t use this approach, then code written in Page_PreInit event of BasePage class has to be copied on all the web-pages of my web-site.

STEP# 2:
Next step is to make changes in master page that you will be using as template for other web-pages.
You need to make changes in Page_Load event and ddlThemes_SelectedIndexChanged event.

//Changes in Master Page

protected void Page_Load(object sender, EventArgs e)<o:p></o:p>

{
    if (!IsPostBack)
    {
        this.ddlThemes.SelectedValue = Session["Theme"].ToString() ;
    }
}
<o:p></o:p>
protected void ddlThemes_SelectedIndexChanged(object sender, EventArgs e)<o:p></o:p>

{
    Session["Theme"] = this.ddlThemes.SelectedValue;
    Response.Redirect(Request.Url.ToString());
}


STEP# 3:
Change the content Web-Pages to inherit from BasePage class, for example, as:

public partial class SayHello : MyWebSite.BasePage
{
…
}

I hope this will help you to resolve your problem.
In case you find any problem, please post back.

Good Luck!

Answer 9

User1673739617 posted

 hi,

 NO, the last post from Jeremy did not solve my problem. He gave me an updated global.asax file to upload but i'm still having the same issues...

Will your post above, actually solve my issue, of the skins changing dynamically?

 

my current global.asax code is below, do you see any problems with it?

 <%@ Application Language="VB" %>

<script runat="server">

    Sub Application_Start(ByVal sender As [Object], ByVal e As EventArgs)
        AddHandler SiteMap.SiteMapResolve, AddressOf Me.AppendQueryString
        If (Roles.RoleExists("Administrators") = False) Then
            Roles.CreateRole("Administrators")
        End If
        If (Roles.RoleExists("Friends") = False) Then
            Roles.CreateRole("Friends")
        End If
        
        ' Set our user count to 0 when we start the server
        Application("ActiveUsers") = 0
    End Sub
    
    Sub Session_OnStart(ByVal sender As [Object], ByVal e As EventArgs)
        Session.Timeout = 10
        Session("Start") = Now
        Application.Lock()
        Application("ActiveUsers") = CInt(Application("ActiveUsers")) + 1
        Application.UnLock()
        
    End Sub
    
    Sub Session_OnEnd(ByVal sender As [Object], ByVal e As EventArgs)
        Application.Lock()
        Application("ActiveUsers") = CInt(Application("ActiveUsers")) - 1
        Application.UnLock()
    End Sub

    Function AppendQueryString(ByVal o As [Object], ByVal e As SiteMapResolveEventArgs) As SiteMapNode
        If (Not (SiteMap.CurrentNode) Is Nothing) Then
            Dim temp As SiteMapNode
            temp = SiteMap.CurrentNode.Clone(True)
            Dim u As Uri = New Uri(e.Context.Request.Url.ToString)
            temp.Url = (temp.Url + u.Query)
            If (Not (temp.ParentNode) Is Nothing) Then
                temp.ParentNode.Url = (temp.ParentNode.Url + u.Query)
            End If
            Return temp
        Else
            Return Nothing
        End If
    End Function

</script>

 

 

thanks,

 

ricky

Answer 10

User986106991 posted

Ricky,

Actually i do not have any idea about multiple master pages in your sample application that you are working on.

I think understanding the concept behind mutiple master pages there and
first having a walk-over some Themes and Skins basics from the link:
http://www.code-magazin.de/article.aspx?quickid=0709061&page=5 should surely help you.

After that you can go over my previous post to Change Web-Site Theme at run-time in ASP.Net 2.0

Good Luck!