下面是从Asp.net 后台添加CSS、JS、Meta标签的写法，我们这里写成函数方便以后使用。如果函数放在页面类中， Page参数也可以不要。
首先导入命名空间 using System.Web.UI.HtmlControls;

        /// <summary>
        /// 添加JS脚本链接
        /// </summary>
        /// <param name="page">页面</param>
        /// <param name="url">路径</param>
        public void AddJS(System.Web.UI.Page page, string url)
        {
                HtmlGenericControl jsControl = new HtmlGenericControl("script");
                jsControl.Attributes.Add("type", "text/javascript");
                jsControl.Attributes.Add("src", url);
                page.Header.Controls.Add(jsControl);
        }
        /// <summary>
        /// 添加JS脚本内容
        /// </summary>
        /// <param name="page">页面</param>
        /// <param name="content">脚本内容</param>
        public void AddScript(System.Web.UI.Page page, string content)
        {
                HtmlGenericControl scriptControl = new HtmlGenericControl("script");
                scriptControl.Attributes.Add("type", "text/javascript");
                scriptControl.InnerHtml = content;
                page.Header.Controls.Add(scriptControl);
        }
        /// <summary>
        /// 添加CSS样式链接
        /// </summary>
        /// <param name="page">页面</param>
        /// <param name="url">路径</param>
        public void AddCss(System.Web.UI.Page page, string url)
        {
                HtmlLink link = new HtmlLink();
                link.Href = http://www.mamicode.com/url;
                link.Attributes.Add("rel", "stylesheet");
                link.Attributes.Add("type", "text/css");
                page.Header.Controls.Add(link);
        }
        /// <summary>
        /// 添加CSS样式内容
        /// </summary>
        /// <param name="page">页面</param>
        /// <param name="content">样式内容</param>
        public void AddStyle(System.Web.UI.Page page, string content)
        {
                HtmlGenericControl styleControl = new HtmlGenericControl("style");
                styleControl.Attributes.Add("type", "text/css");
                styleControl.InnerHtml = content;
                page.Header.Controls.Add(styleControl);
        }
        /// <summary>
        /// 添加Meta标签
        /// </summary>
        /// <param name="page">页面</param>
        /// <param name="name">Meta名字</param>
        /// <param name="content">Meta内容</param>
        public void AddMeta(System.Web.UI.Page page, string name, string content)
        {
                HtmlMeta meta = new HtmlMeta();
                meta.Name = name;
                meta.Content = content;
                page.Header.Controls.Add(meta);
        }

Asp.net 后台添加CSS、JS、Meta标签