一、条件查
public List<Users> ss(string ids) { List<Users> ulist=new List<Users>();
声明使用Linq类 using (StudentDataContext con = new StudentDataContext()) { 创建条件 ulist =con.Users.Where(r=>r.Ids.ToString()==ids).ToList(); } return ulist; }
二、高级查
1、以xx开头：
public List<Users> ss(string ids) { List<Users> ulist=new List<Users>(); using (StudentDataContext con = new StudentDataContext()) { //开头方法（“字符串”） ulist = con.Users.Where(r => r.Username.StartsWith("赵")).ToList(); } return ulist; }
2、以xx结尾：
ulist = con.Users.Where(r => r.Username.EndsWith("赵")).ToList();
3、包含xx:
ulist = con.Users.Where(r => r.Username.Contains("赵")).ToList();
4、个数：
（1）有变量接收：ulist.Count;或con.users.Count()
（2）无接受：ulist.Count();
5、最大值：con.Users.Max(r=>r.Ids)
6、最小值：con.Users.Min(r=>r.Ids)
7、平均值：con.Users.Average(r=>r.Ids)
8、求和：con.Users.Sum(r=>r.Ids)
9、排序：
（1）、OrderBy 按升序对值进行排序。 con.Users.OrderBy(r=>r.Ids)
（2）、OrderByDescending 按降序对值进行排序
（3）、ThenBy 按升序执行次要排序。
（4）、ThenByDescending 按降序执行次要排序。
10、分页查询
总共跳转条数 单次显示条数
con.Users.Skip((a - 1) * page).Take(page);
11、组合查询
组合查询是指将前条件查询结果基础上对后集合进行查询
例：
int page = 3; protected void Page_Load(object sender, EventArgs e) { string id = Request["id"]; if (!IsPostBack) { using (StudentDataContext con = new StudentDataContext()) { DropDownList1.DataSource = con.Nation.ToList(); DropDownList1.DataTextField = "NationName"; DropDownList1.DataValueField = "NationCode"; DropDownList1.DataBind(); Users u = con.Users.Where(w => w.Ids.ToString() == id).FirstOrDefault(); if (u == null) { Label4.Text = ""; } else { TextBox1.Text = u.Username; TextBox2.Text = u.Password; TextBox5.Text = u.Password; TextBox3.Text = u.Nikename; if (u.Sex == false) { RadioButtonList1.Items[1].Selected = true; } TextBox4.Text = Convert.ToDateTime(u.Birthday).ToString("yyyy年MM月dd日"); foreach (ListItem li in dr_nation.Items) { if (li.Value == u.Nation) li.Selected = true; } } } } if (Request.Cookies["name"] != null) { string a = HttpUtility.UrlDecode(Request.Cookies["name"].Value, System.Text.Encoding.GetEncoding("utf-8")); Label1.Text ="你好，"+ a; } if (!IsPostBack) { using (StudentDataContext con = new StudentDataContext()) { dr_nation.DataSource = con.Nation.ToList(); dr_nation.DataTextField = "NationName"; dr_nation.DataValueField = "NationCode"; dr_nation.DataBind(); Repeater1.DataSource =con.Users.ToList().Take(page); Repeater1.DataBind(); Label2.Text = "1"; Label3.Text = (Math.Ceiling(Convert.ToDecimal(con.Users.ToList().Count) / page)).ToString(); } } Button1.Click += Button1_Click; bt_first.Click += bt_first_Click; bt_last.Click += bt_last_Click; bt_nex.Click += bt_nex_Click; bt_up.Click += bt_up_Click; } void bt_up_Click(object sender, EventArgs e) { if (Label2.Text == "1") { return; } using (StudentDataContext con = new StudentDataContext()) { int a = Convert.ToInt32(Label2.Text) - 1; Repeater1.DataSource = Data(con).Skip((a - 1) * page).Take(page); Repeater1.DataBind(); Label2.Text = Label3.Text; } } void bt_nex_Click(object sender, EventArgs e) { using (StudentDataContext con = new StudentDataContext()) { if (Label2.Text == (Math.Ceiling(Convert.ToDecimal(Data(con).Count) / page)).ToString()) { return; } int a = Convert.ToInt32(Label2.Text) + 1; Repeater1.DataSource = Data(con).Skip((a - 1) * page).Take(page); Repeater1.DataBind(); Label2.Text = Label3.Text; } } void bt_last_Click(object sender, EventArgs e) { using (StudentDataContext con = new StudentDataContext()) { Repeater1.DataSource = Data(con).Skip((Convert.ToInt32(Label3.Text) - 1) * page).Take(page); Repeater1.DataBind(); Label2.Text = Label3.Text; } } void bt_first_Click(object sender, EventArgs e) { using (StudentDataContext con = new StudentDataContext()) { Repeater1.DataSource = Data(con).Take(page); Repeater1.DataBind(); Label2.Text = "1"; Label3.Text = Data(con).Count.ToString(); } } void Button1_Click(object sender, EventArgs e) { using (StudentDataContext con = new StudentDataContext()) { Repeater1.DataSource = Data(con).Take(page); Repeater1.DataBind(); Label2.Text = "1"; Label3.Text = Data(con).Count.ToString(); } } public List<Users> Data(StudentDataContext con) { List<Users> ulist = new List<Users>(); ulist=con.Users.ToList(); if (name.Text.Trim() != "") { ulist = ulist.Where(w => w.Nikename.Contains(name.Text.Trim())).ToList(); } if(Ra_sex.SelectedValue!="null") { ulist = ulist.Where(w => w.Sex == Convert.ToBoolean(Ra_sex.SelectedValue)).ToList(); } ulist = ulist.Where(w => w.Nation.ToString() == dr_nation.SelectedValue).ToList(); Label3.Text = (Math.Ceiling(Convert.ToDecimal(ulist.Count) / page)).ToString(); con.Connection.Close(); return ulist; }
<asp:Label ID="Label1" runat="server" Text=""></asp:Label><br /> 昵称：<asp:TextBox ID="name" runat="server"></asp:TextBox> 性别：<asp:RadioButtonList ID="Ra_sex" RepeatLayout="Flow" RepeatDirection="Horizontal" runat="server"> <asp:ListItem Text="全部" Value="null" Selected="True"></asp:ListItem> <asp:ListItem Text="男" Value="true"></asp:ListItem> <asp:ListItem Text="女" Value="false"></asp:ListItem> </asp:RadioButtonList> 民族：<asp:DropDownList ID="dr_nation" runat="server"></asp:DropDownList> <asp:Button ID="Button1" runat="server" Text="查询" /> <table style="width: 100%; background-color: blue; text-align: center"> <tr> <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>操作</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("Nikename") %></td> <td><%#Eval("sexstr") %></td> <td><%#Eval("birthdaystr") %></td> <td><%#Eval("nationstr") %></td> <td> <div id="updatebtn" style="float: left;margin-left:10px">编辑</div> <div id="deletebtn" style="float: left;margin-left:10px">删除</div> </td> </tr> </ItemTemplate> </asp:Repeater> </table> 当前第[<asp:Label ID="Label2" runat="server" Text="Label"></asp:Label>]页 共[<asp:Label ID="Label3" runat="server" Text="Label"></asp:Label>]页 <asp:Button ID="bt_first" runat="server" Text="首页" /> <asp:Button ID="bt_up" runat="server" Text="上一页" /> <asp:Button ID="bt_nex" runat="server" Text="下一页" /> <asp:Button ID="bt_last" runat="server" Text="尾页" />
12、集合交集
结构：集合1.Intersect(集合2).Intersect（集合3）.ToList();
例：
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; } }
