Detailed explanation of how MVC generates page number selector to return HTML code?

public string GetPaginationHtml(PaginationViewModel p)
{
    var PageNum = p.Page;//当前页码（页码从1开始）
    var PageCount = p.PageCount;//总页数
    var ItemCount = p.ItemCount;//总条数

    var showPageNum = 6;//显示数字的页面数量

    var html = new StringBuilder();
    html.Append(string.Format("<ul class=&#39;pagination&#39; id=&#39;{0}&#39; data-data=&#39;{1}&#39;>", p.ULID, p.Data));//ULID和Data是方便在前台增加事件用的
    if (PageCount > 1)
    {
        var startPage = 1;
        if (showPageNum > PageCount)
        {
            startPage = 1;
        }
        else
        {
            if (PageNum - (showPageNum / 2) <= 0)
            {
                startPage = 1;
            }
            else if (PageNum + (showPageNum / 2) >= PageCount)
            {
                startPage = PageCount - showPageNum;
            }
            else
            {
                startPage = PageNum - (showPageNum / 2);
            }
        }
        startPage = (startPage == 0 ? 1 : startPage);//第一个开始显示数字的页码
        //上一页按钮
        html.Append(string.Format("<li class=&#39;{0}&#39;>
        <a href=&#39;#&#39; class=&#39;js-pageSelect&#39; data-page=&#39;{1}&#39;>
        <span>上一页</span></a></li>", PageNum <= 1 ? "disabled" : "", PageNum - 1));

        if (startPage > 1)//生成第一页按钮和中间省略号
        {
            html.Append("<li><a class=&#39;js-pageSelect&#39;&#39; href=&#39;#&#39; data-page=&#39;1&#39;>1</a></li>");
            if (startPage > 2)
            {
                html.Append("<li><span>...</span></li>");
            }
        }
        for (int i = startPage; i <= (startPage + showPageNum); i++)//生成页码
        {
            if (i > PageCount)
            {
                break;
            }
            html.Append(string.Format("<li class=&#39;{0}&#39;>
            <a class=&#39;js-pageSelect&#39;&#39; href=&#39;#&#39; data-page=&#39;{1}&#39;>{2}</a></li>", i == PageNum ? "active" : "", i, i));
        }

        //生成最后一页按钮和中间省略号
        int maxShowPage = startPage + showPageNum;
        if (maxShowPage <= PageCount - 1)
        {
            if(maxShowPage <= PageCount - 2)
            {
                html.Append("<li><span>...</span></li>");
            }
            html.Append(string.Format("<li><a class=&#39;js-pageSelect&#39;&#39; href=&#39;#&#39; data-page=&#39;{0}&#39;>{1}</a></li>",PageCount,PageCount));
        }
        //显示下一页按钮
        html.Append(string.Format("<li class=&#39;{0}&#39;><a href=&#39;#&#39; class=&#39;js-pageSelect&#39; data-page=&#39;{1}&#39;>
        <span>下一页</span></a></li>", PageNum >= PageCount ? "disabled" : "", PageNum + 1));
        //显示页码信息
        html.Append(string.Format("<li><span>第{0}页 共{1}页{2}条内容</span></li>", PageNum, PageCount, ItemCount));
    }
    else
    {
        //内容不足一页时显示的内容
        html.Append(string.Format("<li><span>共1页{0}条内容</span></li>", ItemCount));
    }
    return html.ToString();
}

@Html.Action("", new {page = 1,pageSize = 20, ... })

$.ajax({
  url: '/Function/FileArchiveSelectShouWenDengJiTableMessage',
  type: 'post',
  dataType: 'html',
  data: {
    page: page,
    pageSize: pagesize,
    ...
    },
})
.done(function (data) {
  $('#ShouWenPageSelect').html(data);
  InitPageSelectEvent();
});