<%@ Page Language="C#" %>
<asp:content id="MyContent" contentplaceholderid="MyContentPH" 
             runat="server" > 
   <script language="C#" runat="server">
      protected override void OnPreInit(EventArgs e) {
         this.MasterPageFile ="~/MyMasterPage2.master";
         base.OnPreInit(e);
      }
   </script>
   <asp:label id="lbl"          Height="100%"     Width="100%"
              BackColor="Black" ForeColor="White" runat="server" 
              Font-Size="XX-Large">Content of Default.aspx</asp:label>  
</asp:content>