【2017-06-02】Linq高级查询，实现分页组合查询。

1、以XXX开头

2、以XXX结尾

3、模糊查询

4、求个数

5、求最大值

6、求最小值

7、求平均值

8、求和

9、升序

10、降序

11、分页

Skip()跳过多少条

Take()取多少条

12、分页组合查询

界面部分

    <form id="form1" runat="server">
        <div>
            车名：<asp:TextBox ID="txt_carname" runat="server"></asp:TextBox>
            油耗：<asp:DropDownList ID="dr_oil" runat="server">
                <asp:ListItem Text="大于" Value=">"></asp:ListItem>
                <asp:ListItem Text="小于" Value="<"></asp:ListItem>
                <asp:ListItem Text="等于" Value="="></asp:ListItem>
                <asp:ListItem Text="大于等于" Value=">="></asp:ListItem>
                <asp:ListItem Text="大于等于" Value=">="></asp:ListItem>
            </asp:DropDownList>
            <asp:TextBox ID="txt_oil" runat="server"></asp:TextBox>
            价格：<asp:DropDownList ID="dr_price" runat="server">
                <asp:ListItem Text="全部" Value="null"></asp:ListItem>
                <asp:ListItem Text="小于30万" Value=""></asp:ListItem>
                <asp:ListItem Text="30-40万" Value=""></asp:ListItem>
                <asp:ListItem Text="40-50万" Value=""></asp:ListItem>
                <asp:ListItem Text="大于50万" Value=""></asp:ListItem>

               </asp:DropDownList>

            <asp:Button ID="Button1" runat="server" Text="查询" />
            <table style="width: 100%; background-color: navy; text-align: center">
                <tr style="height: 40px; color: white;">
                    <td>id</td>
                    <td>编号</td>
                    <td>车名</td>
                    <td>油耗</td>
                    <td>马力</td>
                    <td>价格</td>
                </tr>
                <asp:Repeater ID="Repeater1" runat="server">
                    <ItemTemplate>
                        <tr style="background-color: white;">
                            <td><%#Eval("ids") %></td>
                            <td><%#Eval("code") %></td>
                            <td><%#Eval("name") %></td>
                            <td><%#Eval("oil") %></td>
                            <td><%#Eval("powers") %></td>
                            <td><%#Eval("price") %></td>
                        </tr>
                    </ItemTemplate>
                </asp:Repeater>
            </table>
            当前第【 <asp:Label ID="lab_nownumber" runat="server" Text=""></asp:Label> 】页，一共【 <asp:Label ID="lab_maxnumber" runat="server" Text=""></asp:Label> 】页。
            <asp:Button ID="btn_first" runat="server" Text="首页" /><asp:Button ID="btn_prev" runat="server" Text="上一页" /><asp:Button ID="btn_next" runat="server" Text="下一页" /><asp:Button ID="btn_last" runat="server" Text="尾页" />
        </div>
    </form>

后台代码

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

public partial class Main : System.Web.UI.Page
{
    int PageCount = ;
    protected void Page_Load(object sender, EventArgs e)
    {
        Button1.Click += Button1_Click;
        btn_first.Click += btn_first_Click;
        btn_next.Click += btn_next_Click;
        btn_prev.Click += btn_prev_Click;
        btn_last.Click += btn_last_Click;
        if (!IsPostBack)
        {
            using (Data0216DataClassesDataContext con = new Data0216DataClassesDataContext())
            {
                Repeater1.DataSource = Data().Skip().Take(PageCount);
                Repeater1.DataBind();
                lab_maxnumber.Text = Max().ToString();
            }
        }
    }

    void btn_last_Click(object sender, EventArgs e)
    {
        Repeater1.DataSource = Data().Skip((Max() - ) * PageCount);
        Repeater1.DataBind();
        lab_nownumber.Text = Max().ToString();
        lab_maxnumber.Text = Max().ToString();
    }

    void btn_prev_Click(object sender, EventArgs e)
    {
        int a = Convert.ToInt32(lab_nownumber.Text) - ;
        if (a > )
        {
            Repeater1.DataSource = Data().Skip((a - ) * PageCount).Take(PageCount);
            Repeater1.DataBind();
            lab_nownumber.Text = a.ToString();
            lab_maxnumber.Text = Max().ToString();
        }
    }

    void btn_next_Click(object sender, EventArgs e)
    {
        int a = Convert.ToInt32(lab_nownumber.Text) + ;
        if (a <= Max())
        {
            Repeater1.DataSource = Data().Skip((a - ) * PageCount).Take(PageCount);
            Repeater1.DataBind();
            lab_nownumber.Text = a.ToString();
            lab_maxnumber.Text = Max().ToString();
        }
    }

    void btn_first_Click(object sender, EventArgs e)
    {
        Repeater1.DataSource = Data().Skip().Take(PageCount);
        Repeater1.DataBind();
        lab_nownumber.Text = "";
        lab_maxnumber.Text = Max().ToString();
    }

    void Button1_Click(object sender, EventArgs e)
    {
        Repeater1.DataSource = Data().Skip().Take(PageCount);
        Repeater1.DataBind();
        lab_nownumber.Text = "";
        lab_maxnumber.Text = Max().ToString();
    }

    public List<car> Data()
    {

        using (Data0216DataClassesDataContext con = new Data0216DataClassesDataContext())
        {
            List<car> clist = con.car.ToList();

            if (txt_carname.Text.Trim().Length > )
            {
                clist = clist.Where(r => r.name.Contains(txt_carname.Text.Trim())).ToList();
            }

            if (txt_oil.Text.Trim().Length > )
            {
                if (dr_oil.SelectedValue == ">")
                    clist = clist.Where(r => r.oil > Convert.ToDecimal(txt_oil.Text)).ToList();
                if (dr_oil.SelectedValue == "<")
                    clist = clist.Where(r => r.oil < Convert.ToDecimal(txt_oil.Text)).ToList();
                if (dr_oil.SelectedValue == ">=")
                    clist = clist.Where(r => r.oil >= Convert.ToDecimal(txt_oil.Text)).ToList();
                if (dr_oil.SelectedValue == "<=")
                    clist = clist.Where(r => r.oil <= Convert.ToDecimal(txt_oil.Text)).ToList();
                if (dr_oil.SelectedValue == "=")
                    clist = clist.Where(r => r.oil == Convert.ToDecimal(txt_oil.Text)).ToList();
            }

            if (dr_price.SelectedValue != "null")
            {
                if (dr_price.SelectedValue == "")
                    clist = clist.Where(r => r.price < ).ToList();
                if (dr_price.SelectedValue == "")
                    clist = clist.Where(r => r.price >=  && r.price < ).ToList();
                if (dr_price.SelectedValue == "")
                    clist = clist.Where(r => r.price >=  && r.price < ).ToList();
                if (dr_price.SelectedValue == "")
                    clist = clist.Where(r => r.price >= ).ToList();
            }
            return clist;
        }
    }
    public int Max()
    {
       return Convert.ToInt32(Math.Ceiling(Convert.ToDecimal(Data().Count) / PageCount));
    }
}