retrieve page theme in masterpage

public partial class SiteMaster : System.Web.UI.MasterPage 

{ 

   private string _theme = "Custom"; 

   public string Theme 

   { get { return _theme; } set { _theme = value; } } 

}  

public class BasePage : System.Web.UI.Page    

{ 

   protected void Page_PreInit(object  sender, EventArgs e) 

   { 

      var siteMaster = this.Master as SiteMaster; 

      if (siteMaster != null && !string.IsNullOrEmpty(siteMaster.Theme)) 

      { Theme = siteMaster.Theme; } 

   } 

}