Code
//本示例讲解了动态加载母版页的实现方法。在实现过程中要注意两个要点：一是在Page_PreInit中设置MasterPageFile属性，二是基母版页类BaseMaster的实现和应用。
<script runat="server">
    public override String TitleName
    {
        get
        {
            return "示例5-4(加载DefaultMasterPage.master)";
        }
    }
void Page_Load(Object sender, EventArgs e)
    {
        if (!Page.IsPostBack)
        {
            string selItem = Request.QueryString["masterpage"];
            ListItem item = DropDownList1.Items.FindByValue(selItem);
            if (item != null)
            {
                item.Selected = true;
            }            
        }
    }
    void SelectedMaster(Object sender, EventArgs e)
    {
        if (DropDownList1.SelectedValue == "dynamic")
        {
            string url = Request.Path + "?masterpage=dynamic";
            Response.Redirect(url);
        }
    }
</script>