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 WS.Webs
{
    /// <summary>
    /// WebForm1 的摘要说明。
    /// </summary>
    public class WebForm1 : System.Web.UI.Page
    {
        protected System.Web.UI.WebControls.DataList datalist1;
        protected System.Web.UI.WebControls.Label LPageCount;
        protected System.Web.UI.WebControls.Label LRecordCount;
        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.Label LCurrentPage;
        protected System.Web.UI.WebControls.TextBox gotoPage;
        //自定义分页码记录
        const int PageSize=20;
        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(!Page.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 fdcproject",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["DSN2"]);
            MyConnection.Open();
            return MyConnection;
        }

        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 fdcproject where projid not in(select top "+PageSize*CurrentPage+" projid from fdcproject order by projid asc) order by projid 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();
        }











        Web 窗体设计器生成的代码

        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>");
            }



        
        }

        private void Page_OnClick(object sender, System.EventArgs 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 = ((LinkButton)sender).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()
        }


    }
}