1、linq分页和组合查询：（用项目实战来解释）
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %> <!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> </head> <body> <form id="form1" runat="server"> 用户名：<asp:TextBox ID="txt_uname" runat="server"></asp:TextBox> 昵称：<asp:TextBox ID="txt_nick" runat="server"></asp:TextBox> 性别：<asp:DropDownList ID="dr_sex" runat="server"> <asp:ListItem Text="男" Value="True"></asp:ListItem> <asp:ListItem Text="女" Value="False"></asp:ListItem> <asp:ListItem Text="全部" Value="null"></asp:ListItem> </asp:DropDownList> <asp:Button ID="Button1" runat="server" Text="查询" /> <table style="100%;text-align:center;background-color:navy;"> <tr style="color:white;"> <td>编号</td> <td>用户名</td> <td>密码</td> <td>昵称</td> <td>性别</td> <td>生日</td> <td>民族</td> <td>编辑</td> </tr> <asp:Repeater ID="Repeater1" runat="server"> <ItemTemplate> <tr style="background-color:white;"> <td><%#Eval("ids") %></td> <td><%#Eval("username") %></td> <td><%#Eval("password") %></td> <td><%#Eval("nickname") %></td> <td><%#Eval("sex") %></td> <td><%#Eval("birthday") %></td> <td><%#Eval("nation") %></td> <td> <a href="update.aspx?id=<%#Eval("ids") %>">修改</a> <a href="delete.aspx?id=<%#Eval("ids") %>">删除</a> </td> </tr> </ItemTemplate> </asp:Repeater> </table> 当前第【<asp:Literal ID="lit_nownumber" Text="1" runat="server"></asp:Literal>】页， 共【<asp:Literal ID="lit_max" runat="server"></asp:Literal>】页 <asp:Button ID="btn_prev" runat="server" Text="上一页" /> <asp:Button ID="btn_next" runat="server" Text="下一页" /> </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 _Default : System.Web.UI.Page { int pagecount = 2; protected void Page_Load(object sender, EventArgs e) { Button1.Click += Button1_Click; btn_next.Click += btn_next_Click; btn_prev.Click += btn_prev_Click; if(!IsPostBack) { //using(masterDataContext con=new masterDataContext()) //{ Repeater1.DataSource = data().Take(pagecount); Repeater1.DataBind(); //List<users> ulist = con.users.ToList(); //Repeater1.DataSource = ulist.Skip(0).Take(pagecount); //排序：升序 // Repeater1.DataSource = ulist.OrderBy(r=>r.ids); //排序：降序 //Repeater1.DataSource = ulist.OrderByDescending(r=>Convert.ToDecimal(r.password)); //开头： //Repeater1.DataSource = con.users.Where(r=>r.nickname.StartsWith("王")); //结尾： //Repeater1.DataSource = con.users.Where(r => r.nickname.EndsWith("六")); //模糊查（包含）： //Repeater1.DataSource = con.users.Where(r=>r.nickname.Contains("a")); //个数： //Response.Write("总个数：" + ulist.Count+"<br/>"); // //最大值： //Response.Write("最大值：" + ulist.Max(r => Convert.ToDecimal(r.password)) + "<br/>"); // //最小值： //Response.Write("最小值：" + ulist.Min(r => Convert.ToDecimal(r.password)) + "<br/>"); // //平均值： //Response.Write("平均值：" + ulist.Average(r =>Convert.ToDecimal( r.password)) + "<br/>"); // //求和： //Response.Write("求和：" + ulist.Sum(r => Convert.ToDecimal(r.password)) + "<br/>"); //Repeater1.DataBind(); //} } } void btn_prev_Click(object sender, EventArgs e) { //using (masterDataContext con = new masterDataContext()) //{ // int a = Convert.ToInt32(lit_nownumber.Text) - 1; // Repeater1.DataSource = con.users.Skip((a - 1) * pagecount).Take(pagecount); // Repeater1.DataBind(); // lit_nownumber.Text = a.ToString(); //} int a = Convert.ToInt32(lit_nownumber.Text) - 1; Repeater1.DataSource = data().Skip((a - 1) * pagecount).Take(pagecount); Repeater1.DataBind(); lit_nownumber.Text = a.ToString(); } void btn_next_Click(object sender, EventArgs e) { //using (masterDataContext con = new masterDataContext()) //{ // int a = Convert.ToInt32(lit_nownumber.Text) + 1; // Repeater1.DataSource = con.users.Skip((a - 1) * pagecount).Take(pagecount); // Repeater1.DataBind(); // lit_nownumber.Text = a.ToString(); //} int a = Convert.ToInt32(lit_nownumber.Text) + 1; Repeater1.DataSource = data().Skip((a-1)*pagecount).Take(pagecount); Repeater1.DataBind(); lit_nownumber.Text = a.ToString(); } void Button1_Click(object sender, EventArgs e) { // using(masterDataContext con=new masterDataContext()) // { // List<users> ulist = con.users.ToList(); //if(txt_uname.Text.Trim().Length>0) //{ // ulist = ulist.Where(r=>r.username.Contains(txt_uname.Text.Trim())).ToList(); //} // if(txt_nick.Text.Trim().Length>0) // { // ulist = ulist.Where(r => r.nickname.Contains(txt_nick.Text.Trim())).ToList(); // } // if(dr_sex.SelectedValue!="null") // { // ulist = ulist.Where(r => r.sex == Convert.ToBoolean(dr_sex.SelectedValue)).ToList(); // } // Repeater1.DataSource = ulist; // Repeater1.DataBind(); // } Repeater1.DataSource = data().Take(pagecount); Repeater1.DataBind(); lit_nownumber.Text = "1"; } public List<users> data() { using (masterDataContext con = new masterDataContext()) { List<users> ulist = con.users.ToList(); if (txt_uname.Text.Trim().Length > 0) { ulist = ulist.Where(r => r.username.Contains(txt_uname.Text.Trim())).ToList(); } if (txt_nick.Text.Trim().Length > 0) { ulist = ulist.Where(r => r.nickname.Contains(txt_nick.Text.Trim())).ToList(); } if (dr_sex.SelectedValue != "null") { ulist = ulist.Where(r => r.sex == Convert.ToBoolean(dr_sex.SelectedValue)).ToList(); } lit_max.Text = Convert.ToInt32(Math.Ceiling(Convert.ToDecimal(ulist.Count) / pagecount)).ToString(); return ulist; } } }
2、取集合交集：
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default2.aspx.cs" Inherits="Default2" %> <!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> </head> <body> <form id="form1" runat="server"> <div> </div> </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 Default2 : System.Web.UI.Page { List<test1> tlist1 = new List<test1>(); List<test1> tlist2 = new List<test1>(); List<test1> tlist3 = new List<test1>(); protected void Page_Load(object sender, EventArgs e) { tlist1.Add(new test1() {code="001", name="张三" }); tlist1.Add(new test1() { code = "002", name = "李四" }); tlist1.Add(new test1() { code = "003", name = "王五" }); tlist2.Add(new test1() { code = "001", name = "张三" }); tlist2.Add(new test1() { code = "004", name = "李四" }); tlist2.Add(new test1() { code = "005", name = "王五" }); tlist3.Add(new test1() { code = "001", name = "张三" }); tlist3.Add(new test1() { code = "006", name = "李四" }); tlist3.Add(new test1() { code = "003", name = "王五" }); List<test1> ttlist = tlist1.Intersect(tlist2).Intersect(tlist3).ToList(); } } public class test1 { public string code { get; set; } public string name { get; set; } }