/// <summary>
        /// 重新分行
        /// </summary>
        /// <param name="startElement"></param>
        /// <param name="endElement"></param>
        /// <returns></returns>
        internal override bool ParticalRefreshLines(
            DomElement startElement,
            DomElement endElement,
            VerticalAlignStyle verticalAlign)
        {
            bool result = base.ParticalRefreshLines(
                startElement,
                endElement,
                verticalAlign);

            _Lines      = null;
            this.Height = this.ContentHeight;
            return(result);
        }
        /// <summary>
        /// 收集各层元素包含的文档行对象
        /// </summary>
        /// <param name="contentElement"></param>
        /// <param name="lines"></param>
        private void FillLines(DomContentElement contentElement, DomContentLineList lines)
        {
            foreach (DomContentLine line in contentElement.PrivateLines)
            {
                if (line.Count == 0)
                {
                    throw new InvalidOperationException("line count = 0 ");
                }

                else
                {
                    lines.Add(line);
                }
            }
        }
 internal void RefreshGlobalLines()
 {
     _Lines = null;
 }