ASP.NET 分页+组合查询 练习

分页和组合查询都是通过拼接SQL语句到数据库查询进行实现

到汽车表(car)中查询 ，汽车表选取了“编号 code”，“车名 name”，“日期 time”，“油耗 oil ”，“马力 powers”这几列

分页查询语句：每页只显示五条数据

 查询前五条数据： select top 5 from car

点击下一页按钮：select top 5 from car where code not in(select top 5 code from car)//第二页的时候通过编号，查询前五条之后的数据，第三页括号里top 10，每加一页跳过前面查过的条数，一次类推，需要定义变量等于1，每次加一页给这个变量重新赋值，让5乘以这个变量

上一页按钮也是用此方法

组合查询语句：根据车名、油耗、和马力查询

根据选中的条件进行拼接SQL语句：select * from car where name like '%xxx%' and oil like '%xxx%' and powers > xxx ;

通过选择的任意条件，进行判断，如果前面条件选中，后面跟and xxx，如果前面条件没选中就直接where xxx

分页和组合查询连起来就是：select top 5 from car where  name like '%xxx%' and oil like '%xxx%' and powers > xxx and  code not in(select top 5 code from car);根据不同的选择条件进行拼接，在数据库写一个查询的方法，将拼接好的SQL语句传参到方法中进行执行，调用此方法在前台显示

代码：

数据库实体类：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

/// <summary>
/// Car 的摘要说明
/// </summary>
public class Car
{
    public Car()
    {
        //
        // TODO: 在此处添加构造函数逻辑
        //
    }

    //封装一个汽车表的实体类
    private string _code;//汽车编号

    public string Code
    {
        get { return _code; }
        set { _code = value; }
    }
    private string _name;//汽车名字

    public string Name
    {
        get { return _name; }
        set { _name = value; }
    }
    private DateTime _time;//出产日期

    public DateTime Time
    {
        get { return _time; }
        set { _time = value; }
    }
    private decimal _oil;//油耗

    public decimal Oil
    {
        get { return _oil; }
        set { _oil = value; }
    }
    private int _powers;//马力

    public int Powers
    {
        get { return _powers; }
        set { _powers = value; }
    }
}

数据库操作类：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Data.SqlClient;
using System.Collections;

/// <summary>
/// CarData 的摘要说明
/// </summary>
public class CarData
{
    SqlConnection conn = null;
    SqlCommand cmd = null;
    public CarData()
    {
        conn = new SqlConnection("server=.;database=netlx;user=sa;pwd=123;");
        cmd = conn.CreateCommand();
    }



    /// <summary>
    /// 查询车辆信息
    /// </summary>
    /// <param name="sql"></param>
    /// <returns></returns>
    public List<Car> select(string sql,Hashtable has) 
    {
        List<Car> list = new List<Car>();
        cmd.CommandText = sql;
        cmd.Parameters.Clear();

        foreach (string s in has.Keys)
        {
            cmd.Parameters.Add(s, has[s]);
        }
        conn.Open();
        SqlDataReader dr = cmd.ExecuteReader();
        if (dr.HasRows) 
        {
            while (dr.Read()) 
            {
                Car cc = new Car();
                cc.Code = dr["code"].ToString();
                cc.Name = dr["name"].ToString();
                cc.Time = Convert.ToDateTime(dr["time"]);
                cc.Oil = Convert.ToDecimal(dr["oil"]);
                cc.Powers = Convert.ToInt32(dr["powers"]);
                list.Add(cc);
            }
        }
        conn.Close();
        return list;
    }
}

页面前台代码：

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default1.aspx.cs" Inherits="Default1" %>

<!DOCTYPE html>

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
    <title></title>
<style type="text/css">
        #Bt {
            position: relative;
            font-family: 黑体;
            font-size: 50px;
            text-align: center;
            letter-spacing: 5px; /*字符间距*/
        }
        #Cx {
        height:30px;
        margin-top:20px;
        }
        table {
            background-color: #07066f;
            width: 100%;
        }

        #Bt1 {
            font-family: 微软雅黑;
            font-size: 25px;
            color: white;
            text-align: center;
        }

        #Nr {
            font-family: 微软雅黑;
            font-size: 25px;
            background-color: white;
            text-align: center;
        }

        td {
            padding: 10px;
        }
    </style>
</head>
<body>
    <div id="Bt">汽车信息展示</div>
    <form id="form1" runat="server">
        <div id="Cx">
            车名：<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
            油耗：<asp:TextBox ID="TextBox2" runat="server"></asp:TextBox>
            
            马力：<asp:DropDownList ID="Tjf" runat="server">
                <asp:ListItem>&gt;</asp:ListItem>
                <asp:ListItem>&lt;</asp:ListItem>
                <asp:ListItem>=</asp:ListItem>
            </asp:DropDownList><asp:TextBox ID="TextBox3" runat="server"></asp:TextBox>
            <asp:Button ID="Select" runat="server" Text="确 定" />
        </div>
        <asp:Repeater ID="Repeater1" runat="server">
            <HeaderTemplate>
                <table>
                    <tr id="Bt1">
                        <td>编号</td>
                        <td>车名</td>
                        <td>日期</td>
                        <td>油耗</td>
                        <td>马力</td>
                    </tr>
            </HeaderTemplate>
            <ItemTemplate>
                <tr id="Nr">
                    <td><%#Eval("Code") %></td>
                    <td><%#Eval("Name") %></td>
                    <td><%#Eval("Time") %></td>
                    <td><%#Eval("Oil") %></td>
                    <td><%#Eval("Powers") %></td>
                </tr>
            </ItemTemplate>
            <FooterTemplate>
                </table>
            </FooterTemplate>
        </asp:Repeater>
        当前是第[<asp:Label ID="Yecode" runat="server" Text="Label"></asp:Label>]页
        <asp:LinkButton ID="First" runat="server">首页</asp:LinkButton>
        <asp:LinkButton ID="Up" runat="server">上一页</asp:LinkButton>
        <asp:LinkButton ID="Down" runat="server">下一页</asp:LinkButton>
        <asp:LinkButton ID="Over" runat="server">末页</asp:LinkButton>
        <asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="true"></asp:DropDownList>
    </form>
</body>
</html>

后台代码：

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

public partial class Default1 : System.Web.UI.Page
{
    int count = 5;
    Hashtable hs = new Hashtable();//创建一个全局的哈希表集合，用来放SQL语句中的条件，防攻击
    protected void Page_Load(object sender, EventArgs e)
    {
        Select.Click += Select_Click;//条件查询的确定按钮
        Down.Click += Down_Click;//下一页按钮点击事件
        Up.Click += Up_Click;//上一页按钮点击事件
        First.Click += First_Click;//首页按钮点击事件
        Over.Click += Over_Click;//末页按钮点击事件
        DropDownList1.SelectedIndexChanged += DropDownList1_SelectedIndexChanged;//下拉列表选中提交事件
        if (IsPostBack == false) 
        {
            Repeater1.DataSource = new CarData().select(TSQL(1),hs);
            Repeater1.DataBind();
            Yecode.Text = "1";
            First.Enabled = false;
            Up.Enabled = false;

            for (int i = 1; i <= MaxNumber(); i++) 
            {
                ListItem li = new ListItem(i.ToString(), i.ToString());
                DropDownList1.Items.Add(li);
            }
        }

    }


    //下拉列表选中提交事件
    void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
    {
        int xy = Convert.ToInt32(DropDownList1.SelectedItem.Value);
        Repeater1.DataSource = new CarData().select(TSQL(xy),hs);
        Repeater1.DataBind();
        Yecode.Text = xy.ToString();
        if (Yecode.Text == "1")
        {
            First.Enabled = false;
            Up.Enabled = false;
            Over.Enabled = true;
            Down.Enabled = true;
        }
        else if (Yecode.Text == MaxNumber().ToString())
        {
            First.Enabled = true;
            Up.Enabled = true;
            Over.Enabled = false;
            Down.Enabled = false;
        }
        else
        {
            First.Enabled = true;
            Up.Enabled = true;
            Over.Enabled = true;
            Down.Enabled = true;
        }
    }



    //末页按钮点击事件
    void Over_Click(object sender, EventArgs e)
    {
        Repeater1.DataSource = new CarData().select(TSQL(MaxNumber()),hs);
        Repeater1.DataBind();
        Yecode.Text = MaxNumber().ToString();
        DropDownList1.SelectedIndex = Convert.ToInt32(Yecode.Text) - 1;
        First.Enabled = true;
        Up.Enabled = true;
        Down.Enabled = false;
        Over.Enabled = false;
    }


    //首页按钮点击事件
    void First_Click(object sender, EventArgs e)
    {
        Repeater1.DataSource = new CarData().select(TSQL(1),hs);
        Repeater1.DataBind();
        Yecode.Text = "1";
        DropDownList1.SelectedIndex = 0;
        First.Enabled = false;
        Up.Enabled = false;
        Down.Enabled = true;
        Over.Enabled = true;
    }


    //上一页按钮点击事件
    void Up_Click(object sender, EventArgs e)
    {
        int Yeshu = Convert.ToInt32(Yecode.Text) - 1;
        Yecode.Text = Yeshu.ToString();
        DropDownList1.SelectedIndex = Convert.ToInt32(Yecode.Text) - 1;
        Repeater1.DataSource = new CarData().select(TSQL(Yeshu),hs);
        Repeater1.DataBind();
        if (Yecode.Text == "1") 
        {
            First.Enabled = false;
            Up.Enabled = false;
        }
        Down.Enabled = true;
        Over.Enabled = true;
    }


    //下一页按钮点击事件
    void Down_Click(object sender, EventArgs e)
    {
        int Yeshu = Convert.ToInt32(Yecode.Text) + 1;
        Yecode.Text = Yeshu.ToString();
        DropDownList1.SelectedIndex = Convert.ToInt32(Yecode.Text) - 1;
        Repeater1.DataSource = new CarData().select(TSQL(Yeshu),hs);
        Repeater1.DataBind();
        if (Yecode.Text == MaxNumber().ToString()) 
        {
            Down.Enabled = false;
            Over.Enabled = false;
        }
        First.Enabled = true;
        Up.Enabled = true;
    }


    //条件查询的确定按钮
    void Select_Click(object sender, EventArgs e)
    { 
        Repeater1.DataSource = new CarData().select(TSQL(1),hs);
        Repeater1.DataBind();
        Yecode.Text = "1";

        //调用组合查询没有进行分页的拼接SQL语句的方法去数据库进行查询
        List<Car> data = new CarData().select(Tsql(),hs);
        if (data.Count <= count)//如果查询到的数据的数量少于每页显示的条数
        {
            First.Enabled = false;//则这些翻页按钮就不可用
            Up.Enabled = false;
            Down.Enabled = false;
            Over.Enabled = false;
            DropDownList1.Items.Clear();//将选择页面的下拉列表清空
            ListItem li = new ListItem("1", "1");//只显示1
            DropDownList1.Items.Add(li);
        }
        else //如果大于每页显示的条数
        {
            //则下一页和末页可用。因为一上来首页和上一页是不可用的，当点击下一页或者末页，就会触发点击事件，则其他按钮就会可用
            Down.Enabled = true;
            Over.Enabled = true;
            DropDownList1.Items.Clear();//将选择页面的下拉列表清空
            for (int i = 1; i <= MaxNumber(); i++) //根据查出来的最大页数，重新赋值
            {
                ListItem li = new ListItem(i.ToString(), i.ToString());
                DropDownList1.Items.Add(li);
            }
        }
    }



    //根据条件拼接一个SQL语句方法
    public string TSQL(int Yeshu) 
    {
        hs.Clear();
        int ccc = 0;
        string f1="";
        string f2="";
        string f3="";
        string sql = "select top "+count+" * from car";
        if (TextBox1.Text != "") 
        {
            sql += " where name like @name ";
            ccc++;
            f1=" where name like @name ";
            hs.Add("@name", "%" + TextBox1.Text + "%");
        }
        if (TextBox2.Text != "") 
        {
            if (ccc > 0)
            {
                sql += " and oil like @oil ";
                f2 = " and oil like @oil "; 
            }
            else 
            {
                sql += " where oil like @oil ";
                f2 = " where oil like @oil ";
            }
            hs.Add("@oil", "%" + TextBox2.Text + "%");
            ccc++;
        }
        if (TextBox3.Text != "") 
        {
            if (ccc > 0)
            {
                sql += " and powers " + Tjf.SelectedItem.Value + " @powers";
                f3=" and powers " + Tjf.SelectedItem.Value + " @powers";
            }
            else 
            {
                sql += " where powers" + Tjf.SelectedItem.Value + " @powers";
                f3=" where powers" + Tjf.SelectedItem.Value + " @powers";
            }
            hs.Add("@powers", TextBox3.Text);
            ccc++;
        }

        //分页语句
        if (ccc > 0)
        {
            sql += " and code not in (select top " + count * (Yeshu - 1) + " code from car " + f1 + f2 + f3 + ")";
        }
        else 
        {
            sql += " where code not in (select top " + count * (Yeshu - 1) + " code from car " + f1 + f2 + f3 + ")";
        }
        return sql;
    }


    //查询所有符合条件的数据
    public string Tsql() 
    {
        hs.Clear();
        int cc = 0;
        string sql = "select * from car";
        if (TextBox1.Text != "")
        {
            sql += " where name like @name ";
            cc++;
            hs.Add("@name", "%" + TextBox1.Text + "%");
        }
        if (TextBox2.Text != "")
        {
            if (cc > 0)
            {
                sql += " and oil like @oil ";
            }
            else
            {
                sql += " where oil like @oil ";
            }
            hs.Add("@oil", "%" + TextBox2.Text + "%");
            cc++;
        }
        if (TextBox3.Text != "")
        {
            if (cc > 0)
            {
                sql += " and powers " + Tjf.SelectedItem.Value + " @powers";
            }
            else
            {
                sql += " where powers" + Tjf.SelectedItem.Value + " @powers";
            }
            hs.Add("@powers", TextBox3.Text);
            cc++;
        }
        return sql;
    }
    //根据上面查找数据的数量，除以每页显示的，得到的结果取上限值，得到的是最大页数
    public int MaxNumber()
    {
        List<Car> ccc = new CarData().select(Tsql(),hs);

        double bbb = ccc.Count / (count * 1.0); //总页数，但是是浮点型
        return Convert.ToInt32(Math.Ceiling(bbb));
    }
}

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原文地址：https://www.cnblogs.com/zyg316/p/5697739.html