Applying Themes in ASP.net At RunTime

Step 1: Under the App_Code folder, we add a class file named Theme.cs:

public class Theme
{
private string _name;
public string Name
{
get { return _name; }
set { _name = value; }
}
public Theme(string name)
{
Name = name;
}
}

Step 2: Under the App_Code folder, we add a ThemeManager class file named ThemeManager.cs. This will list all the available themes under the /App_Themes folder.

using System;
using System.Data;
using System.Configuration;
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.Collections;
using System.Collections.Generic;
using System.IO;
public class ThemeManager
{ #region Theme-Related Method public static List GetThemes()
{
DirectoryInfo dInfo = new DirectoryInfo(System.Web.HttpContext.Current.Server.MapPath("App_Themes"));
DirectoryInfo[] dArrInfo = dInfo.GetDirectories();
List list = new List();
foreach (DirectoryInfo sDirectory in dArrInfo)
{
Theme temp = new Theme(sDirectory.Name);
list.Add(temp);
}
return list;
}
#endregion
}

Step 3: Comment out any pre-defined themes such as in the web.config. You don't need this because the application level default theme will be specified in the BasePage class in Step 6.

Step 4: In you master page, such as Default.master, add a data source and a radiobutton list. You can use a dropdownlist if you would prefer that.



Step 5: In the master page code-behind, such as Default.master.cs, add these methods:

protected void strTheme_DataBound(object sender, EventArgs e) { strTheme.SelectedValue = Page.Theme; } protected void strTheme_SelectedIndexChanged(object sender, EventArgs e) { Session.Add("MyTheme", strTheme.SelectedValue); Server.Transfer(Request.FilePath); }


Step 6: Add the BasePage class under App_Code, and specify the default theme. Here, we use "White".

using System;
using System.Data;
using System.Configuration;
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 class BasePage : System.Web.UI.Page
{
protected override void OnPreInit(EventArgs e)
{ base.OnPreInit(e);
if (Session["MyTheme"] == null)
{ Session.Add("MyTheme", "White");
Page.Theme = ((string)Session["MyTheme"]);
}
else
{ Page.Theme = ((string)Session["MyTheme"]); }
}
}

Step 7: Inherit all the pages using the dynamic theme from BasePage: