字段扩展：
因为Linq已经自动生成了一个对应表明的类来封装字段，所以扩展的时候要建立一个名字相同的类并在class后面加上partial进行扩展。扩展的时候this代表这个表，通过this可以.出这个表中的列名以及相关的外键表的表名。
Linq基本操作：
首先要创建Linq类，把相关的表拖进VS。
然后实例化Linq类，通过类名.表名.ToList();来获取所有数据。.AsQueryable()；是获得这个方法但是还没有执行。
Linq高级查询：
通过类名.表名.where(r=>r.XXX)来进行条件查询。XXX表示点出来的列名，直接在后面.出方法写条件。where换成Count，Max，Min等方法也可以获得相应的结果。
分页：.Skip().Take()方法，前者是跳过的数据的条数，后者为获取的数据的条数。
获取交集：A.Intersect(B);A B都是通过不同条件查询出的数据，此方法可以连续调用无数个。
小练习：
HTML界面：
1 <body>
2 <form id="form1" runat="server">
3 <table>
4 <tr>
5 <td>学生编号</td>
6 <td>学生姓名</td>
7 <td>民族</td>
8 <td>生日</td>
9 <td>科目</td>
10 <td>成绩</td>
11 </tr>
12 <asp:Repeater ID="Repeater1" runat="server">
13 <ItemTemplate>
14 <tr>
15 <td><%#Eval("Scode") %></td>
16 <td><%#Eval("Sname") %></td>
17 <td><%#Eval("Snation") %></td>
18 <td><%#Eval("Sbirthday","{0:yyyy-MM-dd}") %></td>
19 <td><%#Eval("Ssubjectname") %></td>
20 <td><%#Eval("Score","{0:#.##}") %></td>
21 </tr>
22 </ItemTemplate>
23 </asp:Repeater>
24 </table>
25 学生姓名：<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox><br />
26 学生民族：<asp:TextBox ID="TextBox2" runat="server"></asp:TextBox><br />
27 学生生日：<asp:DropDownList ID="DropDownList1" runat="server" AppendDataBoundItems="True">
28 <asp:ListItem>请选择</asp:ListItem>
29 </asp:DropDownList><asp:DropDownList ID="DropDownList2" runat="server" AppendDataBoundItems="True">
30 <asp:ListItem>请选择</asp:ListItem>
31 </asp:DropDownList><asp:DropDownList ID="DropDownList3" runat="server" AppendDataBoundItems="True">
32 <asp:ListItem>请选择</asp:ListItem>
33 </asp:DropDownList><br />
34 所学科目：<asp:TextBox ID="TextBox4" runat="server"></asp:TextBox><br />
35 考试成绩：<asp:DropDownList ID="DropDownList4" runat="server" AppendDataBoundItems="True">
36 <asp:ListItem>请选择</asp:ListItem>
37 <asp:ListItem>></asp:ListItem>
38 <asp:ListItem><</asp:ListItem>
39 <asp:ListItem>=</asp:ListItem>
40 </asp:DropDownList><asp:TextBox ID="TextBox3" runat="server"></asp:TextBox><br />
41 <asp:Button ID="Button1" runat="server" Text="查询" /><br />
42 <asp:LinkButton ID="LinkButton1" runat="server">上一页</asp:LinkButton>
43 <asp:LinkButton ID="LinkButton2" runat="server">下一页</asp:LinkButton>
44 </form>
45 </body>
扩展字段：
1 public partial class Linq_Score
2 {
3 /// <summary>
4 /// 显示学号
5 /// </summary>
6 public string Scode
7 {
8 get { return this.Linq_Student.Student_Code; }
9 }
10 /// <summary>
11 /// 显示名字
12 /// </summary>
13 public string Sname
14 {
15 get { return this.Linq_Student.Student_Name; }
16 }
17 /// <summary>
18 /// 显示民族
19 /// </summary>
20 public string Snation
21 {
22 get { return this.Linq_Student.Linq_Nation.Nation_Name; }
23 }
24 /// <summary>
25 /// 显示生日
26 /// </summary>
27 public DateTime? Sbirthday
28 {
29 get { return this.Linq_Student.Student_Birthday; }
30 }
31 /// <summary>
32 /// 显示课程名称
33 /// </summary>
34 public string Ssubjectname
35 {
36 get { return this.Linq_Subject.Subject_Name; }
37 }
38 }
C#后台：
1 ChangYongDataContext CY = new ChangYongDataContext();
2 protected void Page_Load(object sender, EventArgs e)
3 {
4 Button1.Click += Button1_Click;//点击查询
5 LinkButton1.Click += LinkButton1_Click;//点击上一页
6 LinkButton2.Click += LinkButton2_Click;//点击下一页
7 if (!IsPostBack)
8 {
9 Session["num"] = 0;
10 Session["Count"] = 3;
11 Session["Page"] = 0;
12 Repeater1.DataSource = Linq().Skip(Convert.ToInt32(Session["Page"]) * Convert.ToInt32(Session["Count"])).Take(Convert.ToInt32(Session["Count"]));
13 Repeater1.DataBind();
14 for (int i = 1980; i <= DateTime.Now.Year; i++)
15 {
16 DropDownList1.Items.Add(i.ToString());
17 }
18 for (int i = 1; i <= 12; i++)
19 {
20 DropDownList2.Items.Add(i.ToString());
21 }
22 for (int i = 1; i <= 31; i++)
23 {
24 DropDownList3.Items.Add(i.ToString());
25 }
26 LinkButton1.Enabled = false;
27 }
28 }
29 //下一页
30 void LinkButton2_Click(object sender, EventArgs e)
31 {
32 Session["Page"] = Convert.ToInt32(Session["Page"]) + 1;
33 Repeater1.DataSource = Linq().Skip(Convert.ToInt32(Session["Page"]) * Convert.ToInt32(Session["Count"])).Take(Convert.ToInt32(Session["Count"]));
34 Repeater1.DataBind();
35 if ((Convert.ToInt32(Session["Page"]) + 1) >= Math.Ceiling((Linq().Count / 3.0)))
36 {
37 LinkButton2.Enabled = false;
38 }
39 LinkButton1.Enabled = true;
40 }
41 //上一页
42 void LinkButton1_Click(object sender, EventArgs e)
43 {
44 Session["Page"] = Convert.ToInt32(Session["Page"]) - 1;
45 Repeater1.DataSource = Linq().Skip(Convert.ToInt32(Session["Page"]) * Convert.ToInt32(Session["Count"])).Take(Convert.ToInt32(Session["Count"]));
46 Repeater1.DataBind();
47 if (Convert.ToInt32(Session["Page"]) == 0)
48 {
49 LinkButton1.Enabled = false;
50 }
51 LinkButton2.Enabled = true;
52 }
53 //查询
54 void Button1_Click(object sender, EventArgs e)
55 {
56 Session["Page"] = 0;
57 Session["num"] = 1;
58 Repeater1.DataSource = Linq().Skip(Convert.ToInt32(Session["Page"]) * Convert.ToInt32(Session["Count"])).Take(Convert.ToInt32(Session["Count"]));
59 Repeater1.DataBind();
60 if ((Convert.ToInt32(Session["Page"]) + 1) >= Math.Ceiling((Linq().Count / 3.0)))
61 {
62 LinkButton2.Enabled = false;
63 }
64 else
65 {
66 LinkButton2.Enabled = true;
67 }
68 }
69 /// <summary>
70 /// 查询语句
71 /// </summary>
72 /// <returns></returns>
73 public List<Linq_Score> Linq()
74 {
75 var list1 = CY.Linq_Score.AsQueryable();
76 var list2 = CY.Linq_Score.AsQueryable();
77 var list3 = CY.Linq_Score.AsQueryable();
78 var list4 = CY.Linq_Score.AsQueryable();
79 var list5 = CY.Linq_Score.AsQueryable();
80 if (TextBox1.Text.Trim().Length > 0)
81 {
82 list1 = list1.Where(r => r.Linq_Student.Student_Name.Contains(TextBox1.Text.Trim()));
83 }
84 if (TextBox2.Text.Trim().Length > 0)
85 {
86 list2 = list2.Where(r => r.Linq_Student.Linq_Nation.Nation_Name.Contains(TextBox2.Text.Trim()));
87 }
88 if (Session["num"].ToString() == "1" && (DropDownList1.Text != "请选择" || DropDownList2.Text != "请选择" || DropDownList3.Text != "请选择"))
89 {
90 list3 = CY.Linq_Score.Where(r => r.Linq_Student.Student_Birthday.Value.Year.ToString() == DropDownList1.Text || r.Linq_Student.Student_Birthday.Value.Month.ToString() == DropDownList2.Text || r.Linq_Student.Student_Birthday.Value.Date.ToString() == DropDownList3.Text);
91 }
92 if (TextBox4.Text.Trim().Length > 0)
93 {
94 list4 = list4.Where(r => r.Linq_Subject.Subject_Name == TextBox4.Text.Trim());
95 }
96 if (TextBox3.Text.Trim().Length > 0 && DropDownList4.Text != "请选择")
97 {
98 if (DropDownList4.Text == ">")
99 {
100 list5 = list5.Where(r => r.Score > Convert.ToDecimal(TextBox3.Text));
101 }
102 else if (DropDownList4.Text == "<")
103 {
104 list5 = list5.Where(r => r.Score < Convert.ToDecimal(TextBox3.Text));
105 }
106 else if (DropDownList4.Text == "=")
107 {
108 list5 = list5.Where(r => r.Score == Convert.ToDecimal(TextBox3.Text));
109 }
110 }
111 var list = list1.Intersect(list2).Intersect(list3).Intersect(list4).Intersect(list5);
112 return list.ToList();
113 }
时间： 2024-08-09 02:19:16