通用分页算法一

using System;

namespace CountryPark.DAL
{
    /**//// <summary>
    /// PageList 的摘要说明。
    /// </summary>
    public sealed class PageList
    {
        static PageList()
        {
        }
        
        /**//// <summary>
        /// 分页查询数据记录总数获取
        /// </summary>
        /// <param name="_tbName">----要显示的表或多个表的连接</param>
        /// <param name="_ID">----主表的主键</param>
        /// <param name="_strCondition">----查询条件,不需where</param>        
        /// <param name="_Dist">----是否添加查询字段的 DISTINCT 默认0不添加/1添加</param>
        /// <returns></returns>
        public static string getPageListCounts(string _tbName, string _ID, string _strCondition, int _Dist)
        {            
            //---存放取得查询结果总数的查询语句                    
            //---对含有DISTINCT的查询进行SQL构造
            //---对含有DISTINCT的总数查询进行SQL构造
            string strTmp="", SqlSelect="", SqlCounts="";
            
            if (_Dist == 0)
            {
                SqlSelect = "Select ";
                SqlCounts = "COUNT(*)";
            }
            else
            {
                SqlSelect = "Select DISTINCT ";
                SqlCounts = "COUNT(DISTINCT "+ _ID +")";
            }
            if (_strCondition == string.Empty)
            {
                strTmp = SqlSelect +" @Counts="+ SqlCounts +" FROM "+ _tbName;
            }
            else
            {
                strTmp = SqlSelect +" @Counts="+ SqlCounts +" FROM "+ " Where (1=1) "+ _strCondition; 
            }
            return strTmp;
        }


        /**//// <summary>
        /// 获取分页数据查询SQL
        /// </summary>
        /// <param name="_tbName">----要显示的表或多个表的连接</param>
        /// <param name="_fldName">----要显示的字段列表</param>
        /// <param name="_PageSize">----每页显示的记录个数</param>
        /// <param name="_Page">----要显示那一页的记录</param>
        /// <param name="_PageCount">----查询结果分页后的总页数</param>
        /// <param name="_Counts">----查询到的记录数</param>
        /// <param name="_fldSort">----排序字段列表或条件(如果是多字段排列Sort指代最后一个排序字段的排列顺序(最后一个排序字段不加排序标记)--程序传参如：' SortA Asc,SortB Desc,SortC ')</param>
        /// <param name="_Sort">----排序方法，0为升序，1为降序</param>
        /// <param name="_strCondition">----查询条件,不需where</param>
        /// <param name="_ID">----主表的主键</param>
        /// <param name="_Dist">----是否添加查询字段的 DISTINCT 默认0不添加/1添加</param>
        /// <returns></returns>                                                                           
        public static string getPageListSql(string _tbName, string _fldName, int _PageSize, int _Page, out int _PageCount, int _Counts, string _fldSort, int _Sort, string _strCondition, string _ID, int _Dist)
        {                
            string strTmp=""; //---strTmp用于返回的SQL语句
            string SqlSelect="", strSortType="", strFSortType="";   

            if (_Dist == 0)
            {
                SqlSelect = "Select ";            
            }
            else
            {
                SqlSelect = "Select DISTINCT ";                
            }

            if (_Sort == 0)
            {
                strFSortType = " ASC";
                strSortType = " DESC";
            }
            else
            {
                strFSortType = " DESC";
                strSortType = " ASC";
            }

//            ----取得查询结果总数量-----
            int tmpCounts = 1;
            if (_Counts != 0)
            {
                tmpCounts = _Counts;
            }
//          --取得分页总数
            _PageCount = (tmpCounts + _PageSize - 1)/_PageSize;
            //    /**//**当前页大于总页数 取最后一页**/
            if (_Page > _PageCount)
            {
                _Page = _PageCount; 
            }
            if (_Page <= 0)
            {
                _Page = 1;
            }
//          --/*-----数据分页2分处理-------*/
            int pageIndex = tmpCounts/_PageSize;
            int lastCount = tmpCounts%_PageSize;
            if (lastCount > 0)
            {
                pageIndex = pageIndex + 1;
            }
            else
            {
                lastCount = _PageSize;
            }
            if (_strCondition == string.Empty) // --没有设置显示条件
            {
                if (pageIndex < 2 || _Page <= (pageIndex/2 + pageIndex%2))  //--前半部分数据处理
                {
                    if (_Page == 1)
                    {
                        strTmp = SqlSelect +" TOP "+ _PageSize +" "+ _fldName +" FROM "+ _tbName +" orDER BY "+ _fldSort +" "+ strFSortType;
                    }
                    else
                    {
                        strTmp = SqlSelect +" TOP "+ _PageSize +" "+ _fldName +" FROM "+ _tbName +" Where "+ _ID +" <(Select MIN("+ _ID +") FROM ("+ SqlSelect +" TOP "+ _PageSize*(_Page-1) +" "+ _ID +" FROM "+ _tbName +
                            " orDER BY "+ _fldSort +" "+ strFSortType +") AS TBMinID) orDER BY "+ _fldSort +" "+ strFSortType;
                    }
                }
                else
                {
                    _Page = pageIndex - _Page + 1; //后半部分数据处理
                    if (_Page <= 1) //--最后一页数据显示
                    {
                        strTmp = SqlSelect +" * FROM ("+ SqlSelect +" TOP "+ lastCount +" "+ _fldName +" FROM "+ _tbName +" orDER BY "+ _fldSort +" "+ strSortType +") AS TempTB"+ " orDER BY "+ _fldSort +" "+ strFSortType;
                    }
                    else
                    {
                        strTmp = SqlSelect +" * FROM ("+ SqlSelect +" TOP "+ _PageSize +" "+ _fldName +" FROM "+ _tbName +
                            " Where "+ _ID +" >(Select MAX("+ _ID +") FROM("+ SqlSelect +" TOP "+ (_PageSize*(_Page-2)+lastCount) +" "+ _ID +" FROM "+ _tbName +
                            " orDER BY "+ _fldSort +" "+ strSortType +") AS TBMaxID) orDER BY "+ _fldSort +" "+ strSortType +") AS TempTB orDER BY "+ _fldSort +" "+ strFSortType;
                    }
                }
            }
            else // --有查询条件
            {
                if (pageIndex < 2 || _Page <=(pageIndex/2 + pageIndex%2))//--前半部分数据处理
                {
                    if (_Page == 1)
                    {
                        strTmp = SqlSelect +" TOP "+ _PageSize +" "+ _fldName +" FROM "+ _tbName +"Where 1=1 "+ _strCondition +" orDER BY "+ _fldSort +" "+ strFSortType;
                    }
                    else
                    {
                        strTmp = SqlSelect +" TOP "+ _PageSize +" "+ _fldName +" FROM "+ _tbName +
                            " Where "+ _ID +" <(Select MIN("+ _ID +") FROM ("+ SqlSelect +" TOP "+ (_PageSize*(_Page-1)) +" "+ _ID +" FROM " +_tbName +
                            " Where 1=1 "+ _strCondition +" orDER BY "+ _fldSort +" "+ strFSortType +") AS TBMaxID) "+ _strCondition +
                            " orDER BY "+ _fldSort +" "+ strFSortType;                            
                    }
                }
                else //--后半部分数据处理
                {
                    _Page = pageIndex-_Page+1;
                    if (_Page <= 1) //--最后一页数据显示
                    {
                        strTmp = SqlSelect +" * FROM ("+ SqlSelect +" TOP "+ lastCount +" "+ _fldName +" FROM "+ _tbName +
                            " Where 1=1 "+ _strCondition +" orDER BY "+ _fldSort +" "+ strSortType +") AS TempTB orDER BY "+ _fldSort +" "+ strFSortType;
                    }
                    else
                    {   
                        strTmp = SqlSelect +" * FROM ("+ SqlSelect +" TOP "+ _PageSize +" "+ _fldName +" FROM "+ _tbName +
                            " Where "+ _ID +" >(Select MAX("+ _ID +") FROM("+ SqlSelect +" TOP "+ (_PageSize*(_Page-2)+ lastCount) +" "+ _ID +" FROM "+ _tbName +
                            " Where 1=1 "+ _strCondition +" orDER BY "+ _fldSort +" "+ strSortType +") AS TBMaxID) "+ _strCondition +
                            " orDER BY "+ _fldSort +" "+ strSortType +") AS TempTB orDER BY "+ _fldSort +" "+ strFSortType;
                    }
                }
            }

            return strTmp;
        }
    }
}







public IList getParkDataList(string key, int curPage, out int pageCount, int pageSize, int Counts)
        {
            
            IList list = new ArrayList();

            string SECLECT_FIELD = "T_Park.ParkID, T_Park.ParkTitle, T_Park.ParkLetter, T_ParkArea.AreaName, T_ParkType.ParkTypeName ";
            string SECLECT_TABLE = "T_ParkType INNER JOIN (T_ParkArea INNER JOIN T_Park ON T_ParkArea.ParkAreaID = T_Park.ParkAreaID) ON T_ParkType.ParkTypeID = T_Park.ParkTypeID";
            string SECLECT_CONDITION = string.Empty;


            if (key != string.Empty)
            {
                SECLECT_CONDITION = " AND T_Park.ParkTitle like '%"+ key +"%'";
            }

            string Select_ID = "ParkID";
            string Select_FLDSORT = "ParkID";
            int Select_SORT = 1;
            int Select_DIST = 0;
            string SQL = PageList.getPageListSql(SECLECT_TABLE, SECLECT_FIELD, pageSize, curPage, out pageCount, Counts, Select_FLDSORT, Select_SORT, SECLECT_CONDITION, Select_ID, Select_DIST);
            //string strCondition;        
            OleDb db = new OleDb();
            ParkBE park;            
            using(OleDbDataReader dr = (OleDbDataReader)db.ExecuteReader(CommonFun.GetConnectionString(), CommandType.Text, SQL))
            {
                while (dr.Read())
                {    
                    park = new ParkBE();
                    park.ParkID = Convert.ToInt32(dr[0]);
                    park.ParkTitle = dr[1].ToString();
                    park.ParkLetter = dr[2].ToString();
                    park.ParkAreaName = dr[3].ToString();
                    park.ParkTypeName = dr[4].ToString();
                    list.Add(park);
                }
            }            
            return list;
        }

转自：http://www.cnblogs.com/hertcloud/archive/2006/08/23/484583.html