1.新建一個winform項目。

2.添加一個Linq to Sql 類，命名為Northwind

3.打開服務器資源管理器，將表拖動到linq to sql 類，實體類就由Vs生成了

4.實例化DataContext類

class="brush:csharp;gutter:true;">NorthwindDataContext dc = new NorthwindDataContext();

5.下面就可以使用Linq to Sql啦。

a.查詢Employees所有數據

var ee =
from employee in dc.Employees
select employee;

b.加個Where條件，查詢Employee表所有City=London

var e2 =from employee in dc.Employeeswhere employee.City == "London" select employee;

?

c.查詢EmployeeID<5的數據

var e3 =from employee in dc.Employeeswhere employee.EmployeeID < 5 select employee;

?

d.查詢雇傭日期在1993年1月1日以前的人員。

var e4 =from employee in dc.Employeeswhere employee.HireDate < new DateTime(1993, 1, 1) select employee;

?

e.多個查詢條件

var e5 =from employee in dc.Employeeswhere employee.HireDate < new DateTime(1993, 1, 1) where employee.EmployeeID < 3 select employee;

?

f.like語句

var e6 =from employee in dc.Employeeswhere SqlMethods.Like(employee.FirstName, "%a%") //where employee.FirstName.Contains("a") //等價于 like '%a%' //where employee.FirstName.StartsWith("a") //等價于 like 'a%' //where employee.FirstName.EndsWith("a") //等價于 like '%a' select employee;

?

g.查詢指定的列

var e7 =(from employee in dc.Employees//select new { employee.EmployeeID, employee.FirstName }; select new { 員工編號 = employee.EmployeeID, 員工姓名 = employee.FirstName, 尊稱 = employee.TitleOfCourtesy });

?

h.子查詢

var e8 =from employee in dc.Employeeswhere employee.Orders.Count > 100 select employee;

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i.內連接

/*** 查詢位于倫敦的客戶的訂單* SELECT ** FROM [dbo].[Orders]* INNER JOIN [dbo].[Customers] ON [Customers].[CustomerID] = [Orders].[CustomerID]* WHERE [Customers].[City] = 'London'*/var e9 =from cus in dc.Customers join ord in dc.Orders on cus.CustomerID equals ord.CustomerID where cus.City == "London" select ord;

?

j.增加

Employees m = new Employees();m.LastName = "閃碩"; m.FirstName = "燕"; m.Title = "閃碩標題"; dc.Employees.InsertOnSubmit(m); dc.SubmitChanges();

?

k.修改

var e10 = dc.Employees.FirstOrDefault(employee => employee.LastName == "閃碩");e10.City = "石家莊"; dc.SubmitChanges();

?

l.刪除

var e10 = dc.Employees.FirstOrDefault(employee => employee.LastName == "閃碩");dc.Employees.DeleteOnSubmit(e10);dc.SubmitChanges();

轉載于:https://www.cnblogs.com/caozhenqian/p/4600565.html

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