ASP.NET的分页方法（一）

要做一个关于分页写法的专题，这是今天的第一讲，自制分页，可能有些代码需要优化，希望大家给出一些中肯的建议

前台使用的repeater绑定的数据：

<form id="form1" runat="server">
        <div>
            <ul style="list-style: none">
                <asp:Repeater ID="Repeater1" runat="server">
                    <ItemTemplate>
                        <li><%#Eval("Title") %></li>
                    </ItemTemplate>
                </asp:Repeater>
            </ul>
        </div>

        <div id="pagerwrapper">
            <table id="pager" cellspacing="0">
                <tbody>
                    <tr>
                        <td colspan="5">
                            <%=RePager %>
                            跳转至：<asp:TextBox ID="TxtPager" runat="server"></asp:TextBox>页
                            <asp:Button ID="BtnOk" runat="server" Text="确定" OnClick="BtnOk_Click" />
                        </td>
                    </tr>
                </tbody>
            </table>
        </div>
    </form>

后台代码写法如下：注释已标明：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;
using System.Data.SqlClient;
using System.Configuration;

namespace WebApplication1
{
    public partial class WebForm2 : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            if(!IsPostBack)
            {
                GetDate();
                
            }
            //这样写可以避免第一次加载之后再次加载不显示的问题
            GetPager();
        }
        string ConStr = ConfigurationManager.ConnectionStrings["Connection"].ToString();

        public string pager = string.Empty;
        public string RePager = string.Empty;
        int startcount = 0;
        int endcount = 0;
        //绑定数据源
        public void GetDate() 
        {
            if (Request.QueryString["pager"] != null)
            {
                string GetDateSql = "SELECT * FROM ( SELECT ROW_NUMBER() over(order by id) as pid,*FROM [Info]) AS aa where aa.pid>=" + Request.QueryString["pager"] + "";

                using (SqlConnection conn = new SqlConnection(ConStr))
                {
                    conn.Open();
                    DataSet dt = new DataSet();
                    SqlDataAdapter sdt = new SqlDataAdapter(GetDateSql, conn);
                    sdt.Fill(dt);
                    this.Repeater1.DataSource = dt;
                    this.Repeater1.DataBind();
                }
            }
            else 
　　　　　　　//初次加载不传入任何页码，默认显示前十条
            {
                string GetDateSql = "SELECT * FROM ( SELECT ROW_NUMBER() over(order by id) as pid,*FROM [Info]) AS aa ";

                using (SqlConnection conn = new SqlConnection(ConStr))
                {
                    conn.Open();
                    DataSet dt = new DataSet();
                    SqlDataAdapter sdt = new SqlDataAdapter(GetDateSql, conn);
                    sdt.Fill(dt);
                    this.Repeater1.DataSource = dt;
                    this.Repeater1.DataBind();
                }
            }
            
        }
        //得到页码
        public void GetPager() 
        {
            string GetTotal = "SELECT COUNT(*) FROM [Info]";
            using (SqlConnection conn = new SqlConnection(ConStr))
            {
                conn.Open();
                SqlCommand comm = new SqlCommand(GetTotal,conn);
                int i = Convert.ToInt32(comm.ExecuteScalar());
                int totalPageNum = (i + 10 - 1) / 10;//一共的页数
                int j = 0;//记录当前页
                string FirstPager = string.Empty;//首页
                string LastPager = string.Empty;//尾页

                string NextPager = string.Empty;//下一页
                string PrePager = string.Empty;//上一页

                int next = 0;//记录下一页页码
                int pre = 0;//记录上一页页码



                for (j = 1; j <= totalPageNum; j++)
                {
                    //Request.QueryString["value"]接受的是页码值
                    if (Request.QueryString["value"] == null)
                    {
                        startcount = (1 + 5) > totalPageNum ? totalPageNum - 9 : 1 - 4;//中间页起始序号
                        //中间页终止序号
                        endcount = 1 < 5 ? 10 : 1 + 5;
                        if (startcount < 1) { startcount = 1; } //为了避免输出的时候产生负数，设置如果小于1就从序号1开始
                        if (totalPageNum < endcount) { endcount = totalPageNum; } //页码+5的可能性就会产生最终输出序号大于总页码，那么就要将其控制在页码数之内
                    }
                    else 
                    {
                        startcount = (int.Parse(Request.QueryString["value"]) + 5) > totalPageNum ? totalPageNum - 9 : int.Parse(Request.QueryString["value"]) - 4;//中间页起始序号
                        //中间页终止序号
                        endcount = int.Parse(Request.QueryString["value"]) < 5 ? 10 : int.Parse(Request.QueryString["value"]) + 5;
                        if (startcount < 1) { startcount = 1; } //为了避免输出的时候产生负数，设置如果小于1就从序号1开始
                        if (totalPageNum < endcount) { endcount = totalPageNum; } //页码+5的可能性就会产生最终输出序号大于总页码，那么就要将其控制在页码数之内
                    }
                }


                if (Request.QueryString["value"] == null)
                {
                    next = 1 + 1;
                    pre = 1;
                }
                else 
                {
                    next = int.Parse(Request.QueryString["value"]) + 1;
                    pre = int.Parse(Request.QueryString["value"]) - 1;
                    //判断并进行越界处理
                    if(pre<=0)
                    {
                        pre = 1;
                    }
                    if(next>totalPageNum)
                    {
                        next = totalPageNum;
                    }
                }

                for (j = startcount; j <= endcount; j++)
                {
                    if (Request.QueryString["value"]==null)
                    {
                        pager += "<a class=\"hrefName\" href=\"WebForm2.aspx?pager=" + 10 * (1 - 1) + "&value=" + 1 + "\">" + j + "</a>|";
                    }
                    else if (int.Parse(Request.QueryString["value"]) == j)
                    {
                        pager += "<a class=\"hrefName\" href=\"WebForm2.aspx?pager=" + 10 * (j - 1) + "&value=" + j + "\"><span style=\"color:red\">" + j + "</span></a>|";
                    }
                    else
                    {
                        //10 * (j - 1)这个公式的意思是（当前页码-1）*10，可以跳转到对应页码查看相关的数据
                        pager += "<a class=\"hrefName\" href=\"WebForm2.aspx?pager=" + 10 * (j - 1) + "&value=" + j + "\">" + j + "</a>|";
                    }
                }

                FirstPager = "<a class=\"hrefName\" href=\"WebForm2.aspx?pager=" + 10 * (1 - 1) + "&value=" + 1 + "\"> 首页</a>|";
                LastPager = "<a class=\"hrefName\" href=\"WebForm2.aspx?pager=" + 10 * (totalPageNum - 1) + "&value=" + totalPageNum + "\"> 尾页</a>|";
                NextPager = "<a class=\"hrefName\" href=\"WebForm2.aspx?pager=" + 10 * (next - 1) + "&value=" + next + "\"> 下一页</a>|";
                PrePager = "<a class=\"hrefName\" href=\"WebForm2.aspx?pager=" + 10 * (pre - 1) + "&value=" + pre + "\"> 上一页</a>|";

                RePager = FirstPager + PrePager+ pager + NextPager + LastPager;//拼凑字符串
            }
        }
        //跳转到第几页的方法
        protected void BtnOk_Click(object sender, EventArgs e)
        {
            if (Request.QueryString["value"] == null)
            {
                Response.Redirect("WebForm2.aspx?pager=" + 10 * (Convert.ToInt32(this.TxtPager.Text) - 1)+"&value=" + this.TxtPager.Text );
            }
        }
    }
}

 附带几条公式，如有不对，希望大家指正

信息条数/每页显示条数=一共的页数

开始页码= (当前显示页+ 5) > 总页? 总页 - 9 : 当前显示页 - 4;//中间页起始序号
//中间页终止序号
结束页码= 当前显示页 < 5 ? 10 : 当前显示页+ 5;