datalist海量数据表高效率分页算法(不使用存储过程)
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
算
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>");
}
}
}
}
