/// <summary>
        /// 添加样式表
        /// </summary>
        /// <param name="url">样式 URL.</param>
        /// <param name="media"> media 类型.</param>
        /// <param name="position">The position.</param>
        public void AddStyle(string url, HtmlLinkMedia media, StyleRelativePosition position)
        {
            if (GlobalSettings.IsNullOrEmpty(url))
            {
                return;
            }
            HttpContext context    = HttpContext.Current;
            Queue       styleQueue = context.Items[styleKey] as Queue;

            if (styleQueue == null)
            {
                styleQueue = new Queue();
                context.Items[styleKey] = styleQueue;
            }
            styleQueue.Enqueue(new StyleQueueItem(string.Format(styleFormat,
                                                                GlobalSettings.EnsureHtmlEncoded(url),
                                                                (media == HtmlLinkMedia.none?"":" media=\"" + media.ToString() + "\"")), position));
        }
 /// <summary>
 /// 添加样式表.
 /// </summary>
 /// <param name="url">样式 Url</param>
 /// <param name="media">media类型.</param>
 public void AddStyle(string url, HtmlLinkMedia media)
 {
     AddStyle(url, media, StyleRelativePosition.Unspecified);
 }