uusing system.collections.generic; sing system; using system.text; /// <summary> /// 构造分页后的sql语句 /// </summary> public static class paginghelper {     /// <summary>     /// 获取分页sql语句，排序字段需要构成唯一记录     /// </summary>     /// <param name="_recordcount">记录总数</param>     /// <param name="_pagesize">每页记录数</param>     /// <param name="_pageindex">当前页数</param>     /// <param name="_safesql">sql查询语句</param>     /// <param name="_orderfield">排序字段，多个则用“,”隔开</param>     /// <returns>分页sql语句</returns>     public static string createpagingsql(int _recordcount, int _pagesize, int _pageindex, string _safesql, string _orderfield)     {         //重新组合排序字段，防止有错误         string[] arrstrorders = _orderfield.split(new char[] { ',' }, stringsplitoptions.removeemptyentries);         stringbuilder sboriginalorder = new stringbuilder(); //原排序字段         stringbuilder sbreverseo教程rder = new stringbuilder(); //与原排序字段相反，用于分页         for (int i = 0; i < arrstrorders.length; i++)         {             arrstrorders[i] = arrstrorders[i].trim();  //去除前后空格             if (i != 0)             {                 sboriginalorder.append(", ");                 sbreverseorder.append(", ");             }             sboriginalorder.append(arrstrorders[i]);             int index = arrstrorders[i].indexof(" "); //判断是否有升降标识             if (index > 0)             {                 //替换升降标识，分页所需                 bool flag = arrstrorders[i].indexof(" desc", stringcomparison.ordinalignorecase) != -1;                 sbreverseorder.appendformat("{0} {1}", arrstrorders[i].remove(index), flag ? "asc" : "desc");             }             else             {                 sbreverseorder.appendformat("{0} desc", arrstrorders[i]);             }         }         //计算总页数         _pagesize = _pagesize == 0 ? _recordcount : _pagesize;         int pagecount = (_recordcount + _pagesize - 1) / _pagesize;         //检查当前页数         if (_pageindex < 1)         {             _pageindex = 1;         }         else if (_pageindex > pagecount)         {             _pageindex = pagecount;         }         stringbuilder sbsql = new stringbuilder();         //第一页时，直接使用top n，而不进行分页查询         if (_pageindex == 1)         {             sbsql.appendformat(" select top {0} * ", _pagesize);             sbsql.appendformat(" from ({0}) as t ", _safesql);             sbsql.appendformat(" order by {0} ", sboriginalorder.tostring());         }         //最后一页时，减少一个top n         else if (_pageindex == pagecount)         {             sbsql.append(" select * from ");             sbsql.append(" ( ");             sbsql.appendformat(" select top {0} * ", _recordcount - _pagesize * (_pageindex - 1));             sbsql.appendformat(" from ({0}) as t ", _safesql);             sbsql.appendformat(" order by {0} ", sbreverseorder.tostring());             sbsql.append(" ) as t ");             sbsql.appendformat(" order by {0} ", sboriginalorder.tostring());         }         //前半页数时的分页         else if (_pageindex < (pagecount / 2 + pagecount % 2))         {             sbsql.append(" select * from ");             sbsql.append(" ( ");             sbsql.appendformat(" select top {0} * from ", _pagesize);             sbsql.append(" ( ");             sbsql.appendformat(" select top {0} * ", _pagesize * _pageindex);             sbsql.appendformat(" from ({0}) as t ", _safesql);             sbsql.appendformat(" order by {0} ", sboriginalorder.tostring());             sbsql.append(" ) as t ");             sbsql.appendformat(" order by {0} ", sbreverseorder.tostring());             sbsql.append(" ) as t ");             sbsql.appendformat(" order by {0} ", sboriginalorder.tostring());         }         //后半页数时的分页         else         {             sbsql.appendformat(" select top {0} * from ", _pagesize);             sbsql.append(" ( ");             sbsql.appendformat(" select top {0} * ", ((_recordcount % _pagesize) + _pagesize * (pagecount - _pageindex)));             sbsql.appendformat(" from ({0}) as t ", _safesql);             sbsql.appendformat(" order by {0} ", sbreverseorder.tostring());             sbsql.append(" ) as t ");             sbsql.appendformat(" order by {0} ", sboriginalorder.tostring());         }         return sbsql.tostring();     }     /// <summary>     /// 获取记录总数sql语句     /// </summary>     /// <param name="_n">限定记录数</param>     /// <param name="_safesql">sql查询语句</param>     /// <returns>记录总数sql语句</returns>     public static string createtopnsql(int _n, string _safesql)     {         return string.format(" select top {0} * from ({1}) as t ", _n, _safesql);     }     /// <summary>     /// 获取记录总数sql语句     /// </summary>     /// <param name="_safesql">sql查询语句</param>     /// <returns>记录总数sql语句</returns>     public static string createcountingsql(string _safesql)     {         return string.format(" select count(1) as recordcount from ({0}) as t ", _safesql);     } }