通过使用存储过程自定义操作
存储过程代表用于重写默认行为的常见方法。 本主题中的示例演示了如何将生成的方法包装用于存储过程，以及如何直接调用存储过程。
如果使用的是 Visual Studio，可以使用对象关系设计器指定存储过程来执行插入、更新和删除。
备注
若要读回数据库生成的值，请在存储过程中使用输出参数。 如果无法使用输出参数，则编写分部方法实现，而不是依靠 O/R 设计器生成的重写。 在成功完成 INSERT 或 UPDATE 操作后，必须将映射到数据库生成的值的成员设置为适当的值。 有关详细信息，请参阅开发人员在重写默认行为中的责任。
示例 1
在下面的示例中，假定 Northwind 类包含两个方法，这两个方法可用来调用要用于派生类中的重写的存储过程。
[Function()]
public IEnumerable<Order> CustomerOrders(
[Parameter(Name = "CustomerID", DbType = "NChar(5)")]
string customerID)
{
IExecuteResult result = this.ExecuteMethodCall(this,
((MethodInfo)(MethodInfo.GetCurrentMethod())),
customerID);
return ((IEnumerable<Order>)(result.ReturnValue));
}
[Function()]
public IEnumerable<Customer> CustomerById(
[Parameter(Name = "CustomerID", DbType = "NChar(5)")]
string customerID)
{
IExecuteResult result = this.ExecuteMethodCall(this,
((MethodInfo)(MethodInfo.GetCurrentMethod())),
customerID);
return (IEnumerable<Customer>)(result.ReturnValue);
}
<[Function]()> _
Public Function CustomerOrders( _
<Parameter(Name:="CustomerID", DbType:="NChar(5)")> ByVal _
customerID As String) As IEnumerable(Of Order)
Dim result As IExecuteResult = Me.ExecuteMethodCall(Me, _
(CType(MethodInfo.GetCurrentMethod(), MethodInfo)), _
customerID)
Return CType(result.ReturnValue, IEnumerable(Of Order))
End Function
<[Function]()> _
Public Function CustomerById( _
<Parameter(Name:="CustomerID", DbType:="NChar(5)")> ByVal _
customerID As String) As IEnumerable(Of Customer)
Dim result As IExecuteResult = Me.ExecuteMethodCall(Me, _
CType(MethodInfo.GetCurrentMethod(), MethodInfo), _
customerID)
Return CType(result.ReturnValue, IEnumerable(Of Customer))
End Function
示例 2
下面的类将这些方法用于重写。
public class NorthwindThroughSprocs : Northwind
{
public NorthwindThroughSprocs(string connection) :
base(connection)
{
}
// Override loading of Customer.Orders by using method wrapper.
private IEnumerable<Order> LoadOrders(Customer customer)
{
return this.CustomerOrders(customer.CustomerID);
}
// Override loading of Order.Customer by using method wrapper.
private Customer LoadCustomer(Order order)
{
return this.CustomerById(order.CustomerID).Single();
}
// Override INSERT operation on Customer by calling the
// stored procedure directly.
private void InsertCustomer(Customer customer)
{
// Call the INSERT stored procedure directly.
this.ExecuteCommand("exec sp_insert_customer …");
}
// The UPDATE override works similarly, that is, by
// calling the stored procedure directly.
private void UpdateCustomer(Customer original, Customer current)
{
// Call the UPDATE stored procedure by using current
// and original values.
this.ExecuteCommand("exec sp_update_customer …");
}
// The DELETE override works similarly.
private void DeleteCustomer(Customer customer)
{
// Call the DELETE stored procedure directly.
this.ExecuteCommand("exec sp_delete_customer …");
}
}
Public Class NorthwindThroughSprocs : Inherits Northwind
Sub New()
MyBase.New("")
End Sub
' Override loading of Customer.Orders by using method wrapper.
Private Function LoadOrders(ByVal customer As Customer) As _
IEnumerable(Of Order)
Return Me.CustomerOrders(customer.CustomerID)
End Function
' Override loading of Order.Customer by using method wrapper.
Private Function LoadCustomer(ByVal order As Order) As Customer
Return Me.CustomerById(order.CustomerID).Single()
End Function
' Override INSERT operation on Customer by calling the
' stored procedure directly.
Private Sub InsertCustomer(ByVal customer As Customer)
' Call the INSERT stored procedure directly.
Me.ExecuteCommand("exec sp_insert_customer …")
End Sub
' The UPDATE override works similarly, that is, by
' calling the stored procedure directly.
Private Sub UpdateCustomer(ByVal original As Customer, ByVal _
current As Customer)
' Call the UPDATE stored procedure by using current
' and original values.
Me.ExecuteCommand("exec sp_update_customer …")
End Sub
' The DELETE override works similarly.
Private Sub DeleteCustomer(ByVal customer As Customer)
' Call the DELETE stored procedure directly.
Me.ExecuteCommand("exec sp_delete_customer …")
End Sub
End Class
示例 3
您可以完全像使用 NorthwindThroughSprocs 一样使用 Northwnd。
NorthwindThroughSprocs db = new NorthwindThroughSprocs("");
var custQuery =
from cust in db.Customers
where cust.City == "London"
select cust;
foreach (Customer custObj in custQuery)
// deferred loading of cust.Orders uses the override LoadOrders.
foreach (Order ord in custObj.Orders)
// ...
// Make some changes to customers/orders.
// Overrides for Customer are called during the execution of the
// following:
db.SubmitChanges();
Dim db As New NorthwindThroughSprocs()
Dim custQuery = From cust In db.Customers _
Where cust.City = "London" _
Select cust
For Each custObj In custQuery
' Deferred loading of cust.Orders uses the override LoadOrders.
For Each ord In custObj.Orders
' ...
' Make some changes to customers/orders.
' Overrides for Customer are called during the execution
' of the following:
db.SubmitChanges()
Next
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