ASP.NET WebForms Dynamically Selecting MasterPages

http://www.msjoe.com/2011/03/asp-net-webforms-dynamically-selecting-masterpages/

protected override void OnPreInit(EventArgs e)
        {
            base.OnPreInit(e); 
            string mystr = Request.Browser.Type;
            if (mystr == "IE7")
            {
                this.MasterPageFile = "~/site.master";
            }
            else
            {
                this.MasterPageFile = "~/site1.master";
            }
        }

<%@ Page Title="" Language="C#" AutoEventWireup="true" CodeBehind="Skin.aspx.cs"
    Inherits="JqueryTest.Skin" %>

<asp:content id="Content1" contentplaceholderid="HeadContent" runat="server">
</asp:content>
<asp:content id="Content2" contentplaceholderid="MainContent" runat="server">
123 
</asp:content>