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" %>
             
     
              用户名：
              昵称：
              性别：
                  
                   
                   
                  
              
         
                  
                
       
      
      
               
        
                     
编号
                      
用户名
                      
密码
                      
昵称
                      
性别
                      
生日
                      
民族
                     
编辑
                
                
                     
<%#Eval("ids") %>
                      
<%#Eval("username") %>
                      
<%#Eval("password") %>
                      
<%#Eval("nickname") %>
                      
<%#Eval("sex") %>
                      
<%#Eval("birthday") %>
                      
<%#Eval("nation") %>
                      
                 ">修改                 ">删除             
                
                                       
      
        当前第【
      】页，        共【
      】页        
              
          
     

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
     
       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+"
      
");                //     //最大值：                //Response.Write("最大值：" + ulist.Max(r => Convert.ToDecimal(r.password)) + "
      
");                //     //最小值：                //Response.Write("最小值：" + ulist.Min(r => Convert.ToDecimal(r.password)) + "
      
");                //         //平均值：                //Response.Write("平均值：" + ulist.Average(r =>Convert.ToDecimal( r.password)) + "
      
");                //           //求和：                //Response.Write("求和：" + ulist.Sum(r => Convert.ToDecimal(r.password)) + "
      
");                //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
      
        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
       
         data()     {        using (masterDataContext con = new masterDataContext())        {            List
        
          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" %>
             
     
    
      
        
      
    
     

 

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
     
       tlist1 = new List
      
       ();    List
       
         tlist2 = new List
        
         ();    List
         
           tlist3 = new List
          
           (); 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
           
             ttlist = tlist1.Intersect(tlist2).Intersect(tlist3).ToList(); }}public class test1{ public string code { get; set; } public string name { get; set; }}