SuLei.Common/PagingHelper.cs

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using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace SuLei.Common
{
    /// <summary>  
    /// ROW_NUMBER高效率分页(仅支持MSSQL2005及以上)
    /// </summary>  
    public static class PagingHelper
    {
        /// <summary>
        /// 获取分页SQL语句，默认row_number为关健字，所有表不允许使用该字段名
        /// </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)
        {
            //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;
            }
            //拼接SQL字符串，加上ROW_NUMBER函数进行分页
            StringBuilder newSafeSql = new StringBuilder();
            newSafeSql.AppendFormat("SELECT ROW_NUMBER() OVER(ORDER BY {0}) as row_number,", _orderField);
            newSafeSql.Append(_safeSql.Substring(_safeSql.ToUpper().IndexOf("SELECT") + 6));

            //拼接成最终的SQL语句
            StringBuilder sbSql = new StringBuilder();
            sbSql.Append("SELECT * FROM (");
            sbSql.Append(newSafeSql.ToString());
            sbSql.Append(") AS T");
            sbSql.AppendFormat(" WHERE row_number between {0} and {1}", ((_pageIndex - 1) * _pageSize) + 1, _pageIndex * _pageSize);

            return sbSql.ToString();
        }

        /// <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);
        }