主题 外观样式

添加两个主题文件和样式：Blue Red

在主题应用页面添加一个下拉框 列表值：Blue Red

在主题应用页面的后台代码：

protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
        {
            Session["Theme"] = DropDownList1.SelectedValue.ToString();
            Response.Redirect("YZFoot.aspx?themes=" + Session["Theme"].ToString ());
        }
        protected void Page_PreInit(object sender, EventArgs e)
        {
            string Theme=Request .QueryString ["themes"];
            if (Theme == null)
            {
                Theme = "Blue";
            }
            Page.Theme = Theme;
        }