/// <summary>
 /// Adds a html string at the specified index.
 /// </summary>
 /// <param name="tag">The tag object.</param>
 /// <param name="index">The zero-based index at which item should be inserted.</param>
 public void Append(TagBuilder tag, int index)
 {
     if (tag != null)
     {
         HtmlList.Insert(index, tag.ToString());
     }
 }
 /// <summary>
 /// Adds a html string to the body of the tag at the specified index.
 /// </summary>
 /// <param name="html">The HTML string.</param>
 /// <param name="index">The zero-based index at which item should be inserted.</param>
 public void Append(string html, int index)
 {
     if (html != null)
     {
         HtmlList.Insert(index, html);
     }
 }