public virtual void AddStyle(PlotStyle style)
        {
            if (style == null)
            {
                throw new ArgumentNullException("style");
            }

            if (PlotStyles.Contains(style))
            {
                throw new ArgumentException(string.Format("Style '{0}' already exists.", style.Name));
            }

            var styleNode = this["plot_style"];

            if (styleNode == null)
            {
                throw new NotImplementedException("Create style node if it doesn't exist!");
            }

            style.NodeName = _nextStyleNode.ToString();
            styleNode.ChildNodes.Add(style);
        }
 /// <summary>
 /// 添加样式
 /// </summary>
 /// <param name="style"></param>
 public override void AddStyle(PlotStyle style)
 {
     throw new NotSupportedException("Cannot add styles to .ctb files.");
 }