分页代码示例

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;
        //定义每页显示记录
        const int PageSize = 20;
        //定义几个保存分页参数变量
        int PageCount, RecCount, CurrentPage, Pages, JumpPage;
        private void Page_Load(object sender, System.EventArgs e)
        {
            if (!IsPostBack)
            {
                //通过Calc()函数获取总记录数
                RecCount = Calc();
                //计算总页数（加上OverPage()函数防止有余数造成显示数据不完整）
                PageCount = RecCount / PageSize + OverPage();
                //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["PageCounts"] = RecCount / PageSize - ModPage();
                //保存一个为0的页面索引值到ViewState
                ViewState["PageIndex"] = 0;
                //保存PageCount到ViewState，跳页时判断用户输入数是否超出页码范围
                ViewState["JumpPages"] = PageCount;
                //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;
                }
                //调用数据绑定函数TDataBind()进行数据绑定运算
                TDataBind();
            }
        }
        //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)
        {
            //从ViewState中读取页码值保存到CurrentPage变量中进行参数运算
            CurrentPage = (int)ViewState["PageIndex"];
            //从ViewState中读取总页参数运算
            Pages = (int)ViewState["PageCounts"];
            string cmd = e.CommandName;
            //筛选CommandName
            switch (cmd)
            {
                case "next":
                    CurrentPage++;
                    break;
                case "prev":
                    CurrentPage--;
                    break;
                case "last":
                    CurrentPage = Pages;
                    break;
                default:
                    CurrentPage = 0;
                    break;
            }
            //将运算后的CurrentPage变量再次保存至ViewState
            ViewState["PageIndex"] = CurrentPage;
            //调用数据绑定函数TDataBind()
            TDataBind();
        }
        private void TDataBind()
        {
            //从ViewState中读取页码值保存到CurrentPage变量中进行按钮失效运算
            CurrentPage = (int)ViewState["PageIndex"];
            //从ViewState中读取总页参数进行按钮失效运算
            Pages = (int)ViewState["PageCounts"];
            //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
            {
                //从ViewState中读取可用页数值保存到JumpPage变量中
                JumpPage = (int)ViewState["JumpPages"];
                //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
                {
                    //转换用户输入值保存在int型InputPage变量中
                    int InputPage = Int32.Parse(gotoPage.Text.ToString()) - 1;
                    //写入InputPage值到ViewState["PageIndex"]中
                    ViewState["PageIndex"] = InputPage;
                    //调用数据绑定函数TDataBind()再次进行数据绑定运算
                    TDataBind();
                }
            }
            //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>");
            }
        }
    }
}