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
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.Employees where employee.City == "London" select employee;
c.查詢EmployeeID<5的數據
var e3 = from employee in dc.Employees where 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.Employees where employee.HireDate < new DateTime(1993, 1, 1) select employee;
e.多個查詢條件
var e5 = from employee in dc.Employees where employee.HireDate < new DateTime(1993, 1, 1) where employee.EmployeeID < 3 select employee;
f.like語句
var e6 = from employee in dc.Employees where 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.Employees where employee.Orders.Count > 100 select employee;
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();
練習代碼使用Vs2012，微軟northwnd示例數據庫
代碼下載：http://pan.baidu.com/s/1pJyh0Mn
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