/// <summary>
  /// Pager V1.0
  /// </summary>
  /// <param name="helper">HtmlHelper</param>
  /// <param name="pager">分页信息</param>
  /// <returns></returns>
  public static MvcHtmlString Pager(this HtmlHelper helper, PagerModel pager)
  {
    StringBuilder sbHtmlText = new StringBuilder();
    sbHtmlText.Append("<div style=\"text-align:center\"><nav><ul class=\"pagination\">");
    if (pager.PageIndex <= 1)
    {
      sbHtmlText.Append("<li class=\"disabled\"><a href=\"javascript:void(0)\" aria-label=\"Previous\"><span aria-hidden=\"true\">«</span></a></li>");
    }
    else
    {
      sbHtmlText.AppendFormat("<li><a href=\"javascript:loadData(1)\" aria-label=\"1\"><span aria-hidden=\"true\">«</span></a></li>", pager.PageIndex - 1);
      sbHtmlText.AppendFormat("<li><a href=\"javascript:loadData({0})\">{0}</a></li>", pager.PageIndex - 1);
    }
    sbHtmlText.AppendFormat("<li class=\"active\"><a href=\"javascript:void(0)\">{0}<span class=\"sr-only\">(current)</span></a></li>", pager.PageIndex);
    if (pager.PageIndex >= pager.PageCount)
    {
      sbHtmlText.Append("<li class=\"disabled\"><a href=\"javascript:void(0)\" aria-label=\"Next\"><span aria-hidden=\"true\">»</span></a></li>");
    }
    else
    {
      sbHtmlText.AppendFormat("<li><a href=\"javascript:loadData({0})\">{0}</a></li>", pager.PageIndex + 1);
      sbHtmlText.AppendFormat("<li><a href=\"javascript:loadData({0})\" aria-label=\"Next\"><span aria-hidden=\"true\">»</span></a></li>", pager.PageIndex + 1);
    }
    sbHtmlText.Append("</ul></nav>");
    sbHtmlText.AppendFormat("<div><span>每页有<strong>{0}</strong>条数据，一共有<strong>{1}</strong>页，总计<strong>{2}</strong>条数据</span></div></div>", pager.PageSize, pager.PageCount, pager.TotalCount);
    return MvcHtmlString.Create(sbHtmlText.ToString());
  } 

/// <summary>
  /// Pager V2.0
  /// </summary>
  /// <param name="helper">HtmlHelper</param>
  /// <param name="pager">分页信息</param>
  /// <param name="onPageChange">翻页事件</param>
  /// <returns></returns>
  public static MvcHtmlString Pager(this HtmlHelper helper, PagerModel pager, Func<int, string> onPageChange)
  {
    StringBuilder sbHtmlText = new StringBuilder();
    sbHtmlText.Append("<div style=\"text-align:center\"><nav><ul class=\"pagination\">");
    if (pager.PageIndex <= 1)
    {
      sbHtmlText.Append("<li class=\"disabled\"><a href=\"javascript:void(0)\" aria-label=\"Previous\"><span aria-hidden=\"true\">«</span></a></li>");
    }
    else
    {
      sbHtmlText.AppendFormat("<li><a href=\"{0}\" aria-label=\"Previous\"><span aria-hidden=\"true\">«</span></a></li>", onPageChange(pager.PageIndex - 1));
      sbHtmlText.AppendFormat("<li><a href=\"{0}\">{1}</a></li>", onPageChange(pager.PageIndex - 1), pager.PageIndex - 1);
    }
    sbHtmlText.AppendFormat("<li class=\"active\"><a href=\"javascript:void(0)\">{0}<span class=\"sr-only\">(current)</span></a></li>", pager.PageIndex);
    if (pager.PageIndex >= pager.PageCount)
    {
      sbHtmlText.Append("<li class=\"disabled\"><a href=\"javascript:void(0)\" aria-label=\"Next\"><span aria-hidden=\"true\">»</span></a></li>");
    }
    else
    {
      sbHtmlText.AppendFormat("<li><a href=\"{0}\">{1}</a></li>", onPageChange(pager.PageIndex + 1), pager.PageIndex + 1);
      sbHtmlText.AppendFormat("<li><a href=\"{0}\" aria-label=\"Next\"><span aria-hidden=\"true\">»</span></a></li>", onPageChange(pager.PageIndex + 1));
    }
    sbHtmlText.Append("</ul></nav>");
    sbHtmlText.AppendFormat("<div><span>每页有<strong>{0}</strong>条数据，一共有<strong>{1}</strong>页，总计<strong>{2}</strong>条数据</span></div></div>", pager.PageSize, pager.PageCount, pager.TotalCount);
    return MvcHtmlString.Create(sbHtmlText.ToString());
  } 

/// <summary>
  /// Pager V3.0
  /// </summary>
  /// <param name="helper">HtmlHelper</param>
  /// <param name="pager">分页信息</param>
  /// <param name="onPageChange">翻页地址或事件</param>
  /// <param name="pagerViewName">分页分部视图名称</param>
  /// <param name="displayMode">分页显示模式</param>
  /// <returns></returns>
  public static MvcHtmlString Pager(this HtmlHelper helper, PagerModel pager, Func<int, string> onPageChange, string pagerViewName, PagingDisplayMode displayMode = PagingDisplayMode.Always)
  {
    pager.OnPageChange = onPageChange;
    pager.PagingDisplayMode = displayMode;
    return MvcHtmlString.Create(helper.Partial(pagerViewName, pager).ToHtmlString());
  }