LINQ to SQL提供了一个基础结构(运行时)，用于将关系数据作为对象进行管理.它是.NET Framework 3.5版的一个组件，可以将对象模型的语言集成查询转换为SQL.然后将这些查询发送到数据库以执行.从数据库中获取结果后，LINQ to SQL再次将它们转换为对象.
对于大多数ASP.NET开发人员LINQ to SQL(也称为DLINQ)是语言集成查询的一个令人振奋的部分，因为它允许使用通常的LINQ表达式查询SQL Server数据库中的数据.它还允许更新，删除和插入数据，但它遭受的唯一缺点是它对SQL服务器数据库的限制.但是，LINQ to SQL比ADO.NET有许多好处，比如降低复杂性，减少编码行等等.
下面是一个显示LINQ to SQL执行架构的图表.
第1步 : 与数据库服务器建立新的"数据连接".查看&arrar; Server Explorer&arrar;数据连接&arrar;添加连接
步骤2 : 添加LINQ To SQL类文件
第3步 : 从数据库中选择表并拖放到新的LINQ to SQL类文件中.
第4步 : 将表添加到类文件.
使用LINQ to SQL执行查询的规则类似于标准LINQ查询的规则，即查询是延迟执行还是立即执行.有许多组件在使用LINQ to SQL执行查询时起作用，这些组件如下所示.
LINQ to SQL API : 请求代表应用程序执行查询并将其发送到LINQ to SQL Provider.
LINQ to SQL Provider : 将查询转换为Transact SQL(T-SQL)并将新查询发送到ADO Provider以供执行.
ADO Provider &minus ;执行查询后，将结果以DataReader的形式发送到LINQ to SQL Provider，后者又将其转换为用户对象的形式.
应该注意的是，在执行LINQ to SQL查询之前，通过DataContext类连接数据源至关重要.
C＃
using System;
using System.Linq;
namespace LINQtoSQL {
class LinqToSQLCRUD {
static void Main(string[] args) {
string connectString = System.Configuration.ConfigurationManager.ConnectionStrings["LinqToSQLDBConnectionString"].ToString();
LinqToSQLDataContext db = new LinqToSQLDataContext(connectString);
//Create new Employee
Employee newEmployee = new Employee();
newEmployee.Name = "Michael";
newEmployee.Email = "yourname@companyname.com";
newEmployee.ContactNo = "343434343";
newEmployee.DepartmentId = 3;
newEmployee.Address = "Michael - USA";
//Add new Employee to database
db.Employees.InsertOnSubmit(newEmployee);
//Save changes to Database.
db.SubmitChanges();
//Get new Inserted Employee
Employee insertedEmployee = db.Employees.FirstOrDefault(e ⇒e.Name.Equals("Michael"));
Console.WriteLine("Employee Id = {0} , Name = {1}, Email = {2}, ContactNo = {3}, Address = {4}",
insertedEmployee.EmployeeId, insertedEmployee.Name, insertedEmployee.Email,
insertedEmployee.ContactNo, insertedEmployee.Address);
Console.WriteLine("\nPress any key to continue.");
Console.ReadKey();
}
}
}VB
Module Module1
Sub Main()
Dim connectString As String = System.Configuration.ConfigurationManager.ConnectionStrings("LinqToSQLDBConnectionString").ToString()
Dim db As New LinqToSQLDataContext(connectString)
Dim newEmployee As New Employee()
newEmployee.Name = "Michael"
newEmployee.Email = "yourname@companyname.com"
newEmployee.ContactNo = "343434343"
newEmployee.DepartmentId = 3
newEmployee.Address = "Michael - USA"
db.Employees.InsertOnSubmit(newEmployee)
db.SubmitChanges()
Dim insertedEmployee As Employee = db.Employees.FirstOrDefault(Function(e) e.Name.Equals("Michael"))
Console.WriteLine("Employee Id = {0} , Name = {1}, Email = {2}, ContactNo = {3},
Address = {4}", insertedEmployee.EmployeeId, insertedEmployee.Name,
insertedEmployee.Email, insertedEmployee.ContactNo, insertedEmployee.Address)
Console.WriteLine(vbLf & "Press any key to continue.")
Console.ReadKey()
End Sub
End Module当编译并运行上述C＃或VB代码时，它产生以下结果 :
Emplyee ID = 4, Name = Michael, Email = yourname@companyname.com, ContactNo = 343434343, Address = Michael - USA Press any key to continue.
C＃
using System;
using System.Linq;
namespace LINQtoSQL {
class LinqToSQLCRUD {
static void Main(string[] args) {
string connectString = System.Configuration.ConfigurationManager.ConnectionStrings["LinqToSQLDBConnectionString"].ToString();
LinqToSQLDataContext db = new LinqToSQLDataContext(connectString);
//Get Employee for update
Employee employee = db.Employees.FirstOrDefault(e =>e.Name.Equals("Michael"));
employee.Name = "George Michael";
employee.Email = "yourname@companyname.com";
employee.ContactNo = "99999999";
employee.DepartmentId = 2;
employee.Address = "Michael George - UK";
//Save changes to Database.
db.SubmitChanges();
//Get Updated Employee
Employee updatedEmployee = db.Employees.FirstOrDefault(e ⇒e.Name.Equals("George Michael"));
Console.WriteLine("Employee Id = {0} , Name = {1}, Email = {2}, ContactNo = {3}, Address = {4}",
updatedEmployee.EmployeeId, updatedEmployee.Name, updatedEmployee.Email,
updatedEmployee.ContactNo, updatedEmployee.Address);
Console.WriteLine("\nPress any key to continue.");
Console.ReadKey();
}
}
}VB
Module Module1
Sub Main()
Dim connectString As String = System.Configuration.ConfigurationManager.ConnectionStrings("LinqToSQLDBConnectionString").ToString()
Dim db As New LinqToSQLDataContext(connectString)
Dim employee As Employee = db.Employees.FirstOrDefault(Function(e) e.Name.Equals("Michael"))
employee.Name = "George Michael"
employee.Email = "yourname@companyname.com"
employee.ContactNo = "99999999"
employee.DepartmentId = 2
employee.Address = "Michael George - UK"
db.SubmitChanges()
Dim updatedEmployee As Employee = db.Employees.FirstOrDefault(Function(e) e.Name.Equals("George Michael"))
Console.WriteLine("Employee Id = {0} , Name = {1}, Email = {2}, ContactNo = {3},
Address = {4}", updatedEmployee.EmployeeId, updatedEmployee.Name,
updatedEmployee.Email, updatedEmployee.ContactNo, updatedEmployee.Address)
Console.WriteLine(vbLf & "Press any key to continue.")
Console.ReadKey()
End Sub
End Module当编译并运行上述C＃或Vb代码时，它会产生以下结果 :
Emplyee ID = 4, Name = George Michael, Email = yourname@companyname.com, ContactNo = 999999999, Address = Michael George - UK Press any key to continue.
C＃
using System;
using System.Linq;
namespace LINQtoSQL {
class LinqToSQLCRUD {
static void Main(string[] args) {
string connectString = System.Configuration.ConfigurationManager.ConnectionStrings["LinqToSQLDBConnectionString"].ToString();
LinqToSQLDataContext db = newLinqToSQLDataContext(connectString);
//Get Employee to Delete
Employee deleteEmployee = db.Employees.FirstOrDefault(e ⇒e.Name.Equals("George Michael"));
//Delete Employee
db.Employees.DeleteOnSubmit(deleteEmployee);
//Save changes to Database.
db.SubmitChanges();
//Get All Employee from Database
var employeeList = db.Employees;
foreach (Employee employee in employeeList) {
Console.WriteLine("Employee Id = {0} , Name = {1}, Email = {2}, ContactNo = {3}",
employee.EmployeeId, employee.Name, employee.Email, employee.ContactNo);
}
Console.WriteLine("\nPress any key to continue.");
Console.ReadKey();
}
}
}VB
Module Module1
Sub Main()
Dim connectString As String = System.Configuration.ConfigurationManager.ConnectionStrings("LinqToSQLDBConnectionString").ToString()
Dim db As New LinqToSQLDataContext(connectString)
Dim deleteEmployee As Employee = db.Employees.FirstOrDefault(Function(e) e.Name.Equals("George Michael"))
db.Employees.DeleteOnSubmit(deleteEmployee)
db.SubmitChanges()
Dim employeeList = db.Employees
For Each employee As Employee In employeeList
Console.WriteLine("Employee Id = {0} , Name = {1}, Email = {2}, ContactNo = {3}",
employee.EmployeeId, employee.Name, employee.Email, employee.ContactNo)
Next
Console.WriteLine(vbLf & "Press any key to continue.")
Console.ReadKey()
End Sub
End Module编译上面的C＃或VB代码时运行，它产生以下结果 :
Emplyee ID = 1, Name = William, Email = abc@gy.co, ContactNo = 999999999 Emplyee ID = 2, Name = Miley, Email = amp@esds.sds, ContactNo = 999999999 Emplyee ID = 3, Name = Benjamin, Email = asdsad@asdsa.dsd, ContactNo = Press any key to continue.
