linQ 查询

时间：2016-08-08 12:24:00 阅读：222 评论：0 收藏：0 [点我收藏+]

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1、多条件查询：
并且 &&
或者 ||

var list = con.car.Where(r => r.code == "c014" || r.oil == 8.2m);

2、模糊查询
1.模糊
var list = con.car.Where(r => r.name.Contains("AT"));
2.开头
var list = con.car.Where(r => r.name.StartsWith("皇冠"));
3.结尾
var list = con.car.Where(r => r.name.EndsWith("版"));

3、统计查询
1.总个数
//var count = con.car.Count();
2.最大值
//var Max = con.car.Max(r => r.price);
3.最小值
//var Min = con.car.Min(r => r.price);
4.平均值
//var avg = con.car.Average(r => r.price);

4、分页查询
跳过，获取
int count = 5;
int pagecount = 1;

var list = con.car.Skip(pagecount * count).Take(count);

5、排序查询
升序
//var list = con.car.OrderBy(r => r.price);
降序
//var list = con.car.OrderByDescending(r => r.price);

去重：
var aaa = con.car.Select(r => r.oil).Distinct();

6、外键显示
return this.brand1.brand_name;

7、组合查询
交集
var list = list1.Intersect(list2).Intersect(list3);
-------------------------------------------------------------
var list1 = con.car.AsQueryable();
var list2 = con.car.AsQueryable();
var list3 = con.car.AsQueryable();

if (TextBox1.Text.Trim().Length > 0)
{
list1 = list1.Where(r => r.name.Contains(TextBox1.Text.Trim()));
}
if (TextBox2.Text.Trim().Length > 0)
{
list2 = list2.Where(r => r.brand1.brand_name.Contains(TextBox2.Text.Trim()));
}
if (TextBox3.Text.Trim().Length > 0)
{
list3 = list3.Where(r => r.oil == Convert.ToDecimal(TextBox3.Text.Trim()));
}

var list = list1.Intersect(list2).Intersect(list3);

Repeater1.DataSource = list;
Repeater1.DataBind();

<%@ 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">
        table
        {
            width:100%;
            background-color:blue;
            font-size:20px;
            font-family:微软雅黑;
        }
        #tr_head
        {
            color:white;
        }
        .tr_main
        {
            background-color:white;
        }
    </style>
</head>
<body>
    <form id="form1" runat="server">
        名称：<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
        油耗：<asp:TextBox ID="TextBox2" runat="server"></asp:TextBox>
        价格：<asp:TextBox ID="TextBox3" runat="server"></asp:TextBox>
        <asp:Button ID="Button1" runat="server" Text="查询" />
                <br />
        <asp:Repeater ID="Repeater1" runat="server">
            <HeaderTemplate>
                <table>
                    <tr id="tr_head">
                        <td>编号</td>
                        <td>姓名</td>
                        <td>系别</td>
                        <td>时间</td>
                        <td>油耗</td>
                        <td>排量</td>
                        <td>马力</td>
                        <td>价格</td>
                    </tr>
            </HeaderTemplate>
            <ItemTemplate>
                <tr class="tr_main">
                    <td><%#Eval("code") %></td>
                     <td><%#Eval("name") %></td>
                     <td><%#Eval("brand") %></td>
                    <td><%#Eval("time") %></td>
                     <td><%#Eval("oil") %></td>
                     <td><%#Eval("exhaust") %></td>
                     <td><%#Eval("powers") %></td>
                     <td><%#Eval("price") %></td>
                </tr>
            </ItemTemplate>
            <FooterTemplate>
                </table>
            </FooterTemplate>
        </asp:Repeater>
    </form>
</body>
</html>

using System;
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
{
    mydbDataContext conn = new mydbDataContext();
    protected void Page_Load(object sender, EventArgs e)
    {
        Button1.Click += Button1_Click;
    }

    void Button1_Click(object sender, EventArgs e)
    {
        //查询全部
       //var list = conn.Car;
        //并且
        //var list = conn.Car.Where(r=>r.Oil==8.7m&&r.Powers==130);
        //或者
       // var list = conn.Car.Where(r => r.Oil == 8.7m || r.Powers == 130);
        //模糊查询
        //var list = conn.Car.Where(r=>r.Name.Contains("舒适"));
        //已什么开头
        //var list = conn.Car.Where(r => r.Name.StartsWith("宝马"));
        //已什么结尾
        //var list = conn.Car.Where(r => r.Name.EndsWith("型"));
        //个数，数量
        //var aa = conn.Car.Count();
        //最大
      //var aaaa = conn.Car.Max(r=>r.Price);
        //最小
        //var bbb = conn.Car.Min(r=>r.Price);
        //平均值
       // var ccc = conn.Car.Average(r=>r.Price);
        //分页查询
        //跳过 取出
        //var count = 5;
        //var pagecount = 2;
        //var list = conn.Car.Skip(count * pagecount).Take(count);
        //排序
        //升序
        //var list = conn.Car.OrderBy(r=>r.Price);
        //降序
       // var list = conn.Car.OrderByDescending(r=>r.Price);
        //去重查询
        //var ss = conn.Car.Select(r => r.Oil).Distinct();
        //组合查询
        var list1 = conn.Car.AsQueryable();
        var list2 = conn.Car.AsQueryable();
        var list3 = conn.Car.AsQueryable();
        if(TextBox1.Text.Length>0)
        {
            list1 = conn.Car.Where(r=>r.Name.Contains(TextBox1.Text));
        }
        if (TextBox2.Text.Length > 0)
        {
            list1 = conn.Car.Where(r => r.Oil==Convert.ToDecimal(TextBox2.Text));
        }
        if (TextBox1.Text.Length > 0)
        {
            list1 = conn.Car.Where(r => r.Price==Convert.ToDecimal(TextBox3.Text));
        }

        var list = list1.Intersect(list2).Intersect(list3);

        Repeater1.DataSource = list;
        Repeater1.DataBind();
    }
}