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datalist海量数据表高效率分页算法(不使用存储过程)

2008-07-17 15:10 567 查看
首先创建一张表(要求ID自动编号):

create table redheadedfile(

id int identity(1,1),

filenames nvarchar(20),

senduser nvarchar(20),

primary key(id)

)
然后我们写入50万条记录:

declare @i int

set @i=1

while @i<=500000

begin

      insert into redheadedfile(filenames,senduser) values('我的分页算法','万级分页算法')

      set @i=@i+1

end

GO

用Microsoft Visual Studio .NET 2003创建一张WebForm网页(本人起名webform8.aspx)
前台代码片段如下(webform8.aspx):
<%@ Page language="c#" Codebehind="WebForm8.aspx.cs" AutoEventWireup="false" Inherits="WebApplication6.WebForm8" %>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" >

<HTML>

<HEAD>

    <title>WebForm8</title>

    <meta content="Microsoft Visual Studio .NET 7.1" name="GENERATOR">

    <meta content="C#" name="CODE_LANGUAGE">

    <meta content="JavaScript" name="vs_defaultClientScript">

    <meta content="http://schemas.microsoft.com/intellisense/ie5" name="vs_targetSchema">

</HEAD>

<body MS_POSITIONING="GridLayout">

    <form id="Form1" method="post" runat="server">

     <asp:datalist id="datalist1" AlternatingItemStyle-BackColor="#f3f3f3" Width="100%" CellSpacing="0"

      CellPadding="0" Runat="server">

      <ItemTemplate>

       <table width="100%" border="0" cellspacing="0" cellpadding="0">

        <tr>

         <td width="30%"

align="center"><%#DataBinder.Eval(Container.DataItem,"filenames")%></td>

         <td width="30%"

align="center"><%#DataBinder.Eval(Container.DataItem,"senduser")%></td>

         <td width="30%"

align="center"><%#DataBinder.Eval(Container.DataItem,"id")%></td>

        </tr>

       </table>

      </ItemTemplate>

     </asp:datalist>

     <div align="center">共<asp:label id="LPageCount" Runat="server" ForeColor="#ff0000"></asp:label>页/共

<asp:label id="LRecordCount" Runat="server" ForeColor="#ff0000"></asp:label>记录

      <asp:linkbutton id="Fistpage" Runat="server"

CommandName="0">首页</asp:linkbutton>    <asp:linkbutton id="Prevpage" Runat="server" CommandName="prev">

上一页</asp:linkbutton>    <asp:linkbutton id="Nextpage" Runat="server"

CommandName="next">下一页</asp:linkbutton>    <asp:linkbutton id="Lastpage" Runat="server"

CommandName="last">尾页</asp:linkbutton>    当前第<asp:label id="LCurrentPage" Runat="server"

ForeColor="#ff0000"></asp:label>页    跳页<asp:TextBox ID="gotoPage" Runat="server" Width="30px"

MaxLength="5" AutoPostBack="True"></asp:TextBox></div>

    </form>

</body>

</HTML>
后台代码片段如下(webform8.aspx.cs)
using System;

using System.Collections;

using System.ComponentModel;

using System.Data;

using System.Drawing;

using System.Web;

using System.Web.SessionState;

using System.Web.UI;

using System.Web.UI.WebControls;

using System.Web.UI.HtmlControls;

using System.Data.SqlClient;

using System.Configuration;

namespace WebApplication6

{

/// <summary>

/// WebForm8 的摘要说明。

/// </summary>

public class WebForm8 : System.Web.UI.Page

{

    protected System.Web.UI.WebControls.LinkButton Fistpage;

    protected System.Web.UI.WebControls.LinkButton Prevpage;

    protected System.Web.UI.WebControls.LinkButton Nextpage;

    protected System.Web.UI.WebControls.LinkButton Lastpage;

    protected System.Web.UI.WebControls.DataList datalist1;

    protected System.Web.UI.WebControls.DropDownList mydroplist;

    protected System.Web.UI.WebControls.Label LPageCount;

    protected System.Web.UI.WebControls.Label LRecordCount;

    protected System.Web.UI.WebControls.Label LCurrentPage;

    protected System.Web.UI.WebControls.TextBox gotoPage;

    const int PageSize=20;//定义每页显示记录

    int PageCount,RecCount,CurrentPage,Pages,JumpPage;//定义几个保存分页参数变量

    private void Page_Load(object sender, System.EventArgs e)

    {

     if(!IsPostBack)

     {

      RecCount = Calc();//通过Calc()函数获取总记录数

      PageCount = RecCount/PageSize + OverPage();//计算总页数(加上OverPage()函数防止有余数造成显示

数据不完整)

      ViewState["PageCounts"] = RecCount/PageSize -

ModPage();//保存总页参数到ViewState(减去ModPage()函数防止SQL语句执行时溢出查询范围,可以用存储过程分页算法来理解这句)

      ViewState["PageIndex"] = 0;//保存一个为0的页面索引值到ViewState

      ViewState["JumpPages"] = PageCount;//保存PageCount到ViewState,跳页时判断用户输入数是否超出页

码范围

      //显示LPageCount、LRecordCount的状态

      LPageCount.Text = PageCount.ToString();

      LRecordCount.Text = RecCount.ToString();

      //判断跳页文本框失效

      if(RecCount <= 20)

       gotoPage.Enabled = false;

      TDataBind();//调用数据绑定函数TDataBind()进行数据绑定运算

     }

    }

          //计算余页

    public int OverPage()

    {

     int pages = 0;

     if(RecCount%PageSize != 0)

      pages = 1;

     else

      pages = 0;

     return pages;

    }

          //计算余页,防止SQL语句执行时溢出查询范围

    public int ModPage()

    {

     int pages = 0;

     if(RecCount%PageSize == 0 && RecCount != 0)

      pages = 1;

     else

      pages = 0;

     return pages;

    }

          /*

     *计算总记录的静态函数

     *本人在这里使用静态函数的理由是:如果引用的是静态数据或静态函数,连接器会优化生成代码,去掉动态重定位项(对

海量数据表分页效果更明显)。

     *希望大家给予意见、如有不正确的地方望指正。

    */

    public static int Calc()

    {

     int RecordCount = 0;

     SqlCommand MyCmd = new SqlCommand("select count(*) as co from redheadedfile",MyCon());

     SqlDataReader dr = MyCmd.ExecuteReader();

     if(dr.Read())

      RecordCount = Int32.Parse(dr["co"].ToString());

     MyCmd.Connection.Close();

     return RecordCount;

    }

          //数据库连接语句(从Web.Config中获取)

    public static SqlConnection MyCon()

    {

     SqlConnection MyConnection = new SqlConnection(ConfigurationSettings.AppSettings["DSN"]);

     MyConnection.Open();

     return MyConnection;

    }

          //对四个按钮(首页、上一页、下一页、尾页)返回的CommandName值进行操作

    private void Page_OnClick(object sender, CommandEventArgs e)

    {

     CurrentPage = (int)ViewState["PageIndex"];//从ViewState中读取页码值保存到CurrentPage变量中进行参数运



              Pages = (int)ViewState["PageCounts"];//从ViewState中读取总页参数运算

     string cmd = e.CommandName;

     switch(cmd)//筛选CommandName

     {

      case "next":

       CurrentPage++;

       break;

      case "prev":

       CurrentPage--;

       break;

      case "last":

       CurrentPage = Pages;

       break;

      default:

       CurrentPage = 0;

       break;

     }

     ViewState["PageIndex"] = CurrentPage;//将运算后的CurrentPage变量再次保存至ViewState

     TDataBind();//调用数据绑定函数TDataBind()

    }

    private void TDataBind()

    {

     CurrentPage = (int)ViewState["PageIndex"];//从ViewState中读取页码值保存到CurrentPage变量中进行按钮失

效运算

     Pages = (int)ViewState["PageCounts"];//从ViewState中读取总页参数进行按钮失效运算

     //判断四个按钮(首页、上一页、下一页、尾页)状态

     if (CurrentPage + 1 > 1)

     {

      Fistpage.Enabled = true;

      Prevpage.Enabled = true;

     }

     else

     {

      Fistpage.Enabled = false;

      Prevpage.Enabled = false;

     }

     if (CurrentPage == Pages)

     {

      Nextpage.Enabled = false;

      Lastpage.Enabled = false;

     }

     else

     {

      Nextpage.Enabled = true;

      Lastpage.Enabled = true;

     }

              //数据绑定到DataList控件

     DataSet ds = new DataSet();

     //核心SQL语句,进行查询运算(决定了分页的效率:))

     SqlDataAdapter MyAdapter = new SqlDataAdapter("Select Top "+PageSize+" * from redheadedfile where id

not in(select top "+PageSize*CurrentPage+" id from redheadedfile order by id asc) order by id asc",MyCon());

     MyAdapter.Fill(ds,"news");

     datalist1.DataSource = ds.Tables["news"].DefaultView;

     datalist1.DataBind();

     //显示Label控件LCurrentPaget和文本框控件gotoPage状态

     LCurrentPage.Text = (CurrentPage+1).ToString();

     gotoPage.Text = (CurrentPage+1).ToString();

     //释放SqlDataAdapter

     MyAdapter.Dispose();

    }

    #region Web 窗体设计器生成的代码

    override protected void OnInit(EventArgs e)

    {

     //

     // CODEGEN: 该调用是 ASP.NET Web 窗体设计器所必需的。

     //

     InitializeComponent();

     base.OnInit(e);

    }

  

    /// <summary>

    /// 设计器支持所需的方法 - 不要使用代码编辑器修改

    /// 此方法的内容。

    /// </summary>

    private void InitializeComponent()

    {    

     this.Fistpage.Command += new System.Web.UI.WebControls.CommandEventHandler(this.Page_OnClick);

     this.Prevpage.Command += new System.Web.UI.WebControls.CommandEventHandler(this.Page_OnClick);

     this.Nextpage.Command += new System.Web.UI.WebControls.CommandEventHandler(this.Page_OnClick);

     this.Lastpage.Command += new System.Web.UI.WebControls.CommandEventHandler(this.Page_OnClick);

     this.gotoPage.TextChanged += new System.EventHandler(this.gotoPage_TextChanged);

     this.Load += new System.EventHandler(this.Page_Load);

    }

    #endregion

          //跳页代码

    private void gotoPage_TextChanged(object sender, System.EventArgs e)

    {

     try

     {

      JumpPage = (int)ViewState["JumpPages"];//从ViewState中读取可用页数值保存到JumpPage变量中

      //判断用户输入值是否超过可用页数范围值

      if(Int32.Parse(gotoPage.Text) > JumpPage || Int32.Parse(gotoPage.Text) <= 0)

     

Response.Write("<script>alert('页码范围越界!');location.href='WebForm8.aspx'</script>");

      else

      {

       int InputPage = Int32.Parse(gotoPage.Text.ToString()) - 1;//转换用户输入值保存在int型

InputPage变量中

       ViewState["PageIndex"] = InputPage;//写入InputPage值到ViewState["PageIndex"]中

       TDataBind();//调用数据绑定函数TDataBind()再次进行数据绑定运算

      }

     }

        //捕获由用户输入不正确数据类型时造成的异常

     catch(Exception exp)

     {

      Response.Write("<script>alert('"+exp.Message+"');location.href='WebForm8.aspx'</script>");

     }

    }

}

}
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