ObjectDataSourceDisposingEventHandler Delegado

Definición

Representa el método que controlará el evento ObjectDisposing del control ObjectDataSource.Represents the method that will handle the ObjectDisposing event of the ObjectDataSource control.

public delegate void ObjectDataSourceDisposingEventHandler(System::Object ^ sender, ObjectDataSourceDisposingEventArgs ^ e);
public delegate void ObjectDataSourceDisposingEventHandler(object sender, ObjectDataSourceDisposingEventArgs e);
type ObjectDataSourceDisposingEventHandler = delegate of obj * ObjectDataSourceDisposingEventArgs -> unit
Public Delegate Sub ObjectDataSourceDisposingEventHandler(sender As Object, e As ObjectDataSourceDisposingEventArgs)

Parámetros

sender
Object

El origen del evento, ObjectDataSource.The source of the event, the ObjectDataSource.

e
ObjectDataSourceDisposingEventArgs

Objeto ObjectDataSourceDisposingEventArgs que contiene los datos del evento.An ObjectDataSourceDisposingEventArgs that contains the event data.

Ejemplos

Esta sección contiene dos ejemplos de código.This section contains two code examples. En el primer ejemplo de código se muestra cómo usar un ObjectDataSource control con un objeto comercial y un GridView control para mostrar información.The first code example demonstrates how to use an ObjectDataSource control with a business object and a GridView control to display information. El segundo ejemplo de código proporciona un objeto comercial de nivel intermedio de ejemplo que usa el primer ejemplo de código.The second code example provides an example middle-tier business object that the first code example uses.

En el ejemplo de código siguiente se muestra cómo usar un ObjectDataSource control con un objeto comercial y un GridView control para mostrar información.The following code example demonstrates how to use an ObjectDataSource control with a business object and a GridView control to display information. Puede trabajar con un objeto comercial que es muy caro (en términos de tiempo o recursos) de crear para cada operación de datos que realiza la Página Web.You might work with a business object that is very expensive (in terms of time or resources) to create for every data operation that your Web page performs. Una manera de trabajar con un objeto caro podría ser crear una instancia de él una vez y almacenarlo en caché para las operaciones posteriores en lugar de crearlo y destruirlo para cada operación de datos.One way to work with an expensive object might be to create an instance of it once, and then cache it for subsequent operations instead of creating and destroying it for every data operation. Este ejemplo muestra este patrón.This example demonstrates this pattern. Puede controlar el ObjectCreating evento para comprobar primero la memoria caché de un objeto y, a continuación, crear una instancia, solo si aún no se ha almacenado en la memoria caché.You can handle the ObjectCreating event to check the cache first for an object, and then create an instance, only if one is not already cached. A continuación, controle el ObjectDisposing evento para almacenar en caché el objeto comercial para su uso futuro, en lugar de destruirlo.Then, handle the ObjectDisposing event to cache the business object for future use, instead of destroying it. En este ejemplo, la CancelEventArgs.Cancel propiedad de la ObjectDataSourceDisposingEventArgs clase se establece en true , para indicar ObjectDataSource a que no llame a Dispose en la instancia.In this example, the CancelEventArgs.Cancel property of the ObjectDataSourceDisposingEventArgs class is set to true, to direct the ObjectDataSource to not call Dispose on the instance.

<%@ Import namespace="Samples.AspNet.CS" %>
<%@ Page language="c#" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">

// Instead of creating and destroying the business object each time, the 
// business object is cached in the ASP.NET Cache.
private void GetEmployeeLogic(object sender, ObjectDataSourceEventArgs e)
{
    // First check to see if an instance of this object already exists in the Cache.
    EmployeeLogic cachedLogic;
    
    cachedLogic = Cache["ExpensiveEmployeeLogicObject"] as EmployeeLogic;
    
    if (null == cachedLogic) {
            cachedLogic = new EmployeeLogic();            
    }
        
    e.ObjectInstance = cachedLogic;     
}

private void ReturnEmployeeLogic(object sender, ObjectDataSourceDisposingEventArgs e)
{    
    // Get the instance of the business object that the ObjectDataSource is working with.
    EmployeeLogic cachedLogic = e.ObjectInstance as EmployeeLogic;        
    
    // Test to determine whether the object already exists in the cache.
    EmployeeLogic temp = Cache["ExpensiveEmployeeLogicObject"] as EmployeeLogic;
    
    if (null == temp) {
        // If it does not yet exist in the Cache, add it.
        Cache.Insert("ExpensiveEmployeeLogicObject", cachedLogic);
    }
    
    // Cancel the event, so that the object will 
    // not be Disposed if it implements IDisposable.
    e.Cancel = true;
}
</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
  <head>
    <title>ObjectDataSource - C# Example</title>
  </head>
  <body>
    <form id="Form1" method="post" runat="server">

        <asp:gridview
          id="GridView1"
          runat="server"          
          datasourceid="ObjectDataSource1">
        </asp:gridview>

        <asp:objectdatasource 
          id="ObjectDataSource1"
          runat="server"          
          selectmethod="GetCreateTime"          
          typename="Samples.AspNet.CS.EmployeeLogic"
          onobjectcreating="GetEmployeeLogic"
          onobjectdisposing="ReturnEmployeeLogic" >
        </asp:objectdatasource>        

    </form>
  </body>
</html>
<%@ Import namespace="Samples.AspNet.VB" %>
<%@ Page language="vb" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">

' Instead of creating and destroying the business object each time, the 
' business object is cached in the ASP.NET Cache.
Sub GetEmployeeLogic(sender As Object, e As ObjectDataSourceEventArgs)

    ' First check to see if an instance of this object already exists in the Cache.
    Dim cachedLogic As EmployeeLogic 
    
    cachedLogic = CType( Cache("ExpensiveEmployeeLogicObject"), EmployeeLogic)
    
    If (cachedLogic Is Nothing) Then
            cachedLogic = New EmployeeLogic            
    End If
        
    e.ObjectInstance = cachedLogic
    
End Sub ' GetEmployeeLogic

Sub ReturnEmployeeLogic(sender As Object, e As ObjectDataSourceDisposingEventArgs)
    
    ' Get the instance of the business object that the ObjectDataSource is working with.
    Dim cachedLogic  As EmployeeLogic  
    cachedLogic = CType( e.ObjectInstance, EmployeeLogic)
    
    ' Test to determine whether the object already exists in the cache.
    Dim temp As EmployeeLogic 
    temp = CType( Cache("ExpensiveEmployeeLogicObject"), EmployeeLogic)
    
    If (temp Is Nothing) Then
        ' If it does not yet exist in the Cache, add it.
        Cache.Insert("ExpensiveEmployeeLogicObject", cachedLogic)
    End If
    
    ' Cancel the event, so that the object will 
    ' not be Disposed if it implements IDisposable.
    e.Cancel = True
End Sub ' ReturnEmployeeLogic
</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
  <head>
    <title>ObjectDataSource - VB Example</title>
  </head>
  <body>
    <form id="Form1" method="post" runat="server">

        <asp:gridview
          id="GridView1"
          runat="server"          
          datasourceid="ObjectDataSource1">
        </asp:gridview>

        <asp:objectdatasource 
          id="ObjectDataSource1"
          runat="server"          
          selectmethod="GetCreateTime"          
          typename="Samples.AspNet.VB.EmployeeLogic"
          onobjectcreating="GetEmployeeLogic"
          onobjectdisposing="ReturnEmployeeLogic" >
        </asp:objectdatasource>        

    </form>
  </body>
</html>

En el ejemplo de código siguiente se proporciona un ejemplo de objeto comercial de nivel intermedio que utiliza el ejemplo de código anterior.The following code example provides an example middle-tier business object that the preceding code example uses. El ejemplo de código consta de un objeto comercial básico, definido por la EmployeeLogic clase, que es una clase que mantiene el estado y encapsula la lógica de negocios.The code example consists of a basic business object, defined by the EmployeeLogic class, which is a class that maintains state and encapsulates business logic. Para obtener un ejemplo de trabajo completo, debe compilar este código como una biblioteca y, a continuación, utilizar estas clases desde una página ASP.For a complete working example, you must compile this code as a library, and then use these classes from an ASP page.

namespace Samples.AspNet.CS {

using System;
using System.Collections;
using System.Web.UI;
using System.Web.UI.WebControls;
  //
  // EmployeeLogic is a stateless business object that encapsulates
  // the operations you can perform on a NorthwindEmployee object.
  //
  public class EmployeeLogic {

    public EmployeeLogic () : this(DateTime.Now) {        
    }
    
    public EmployeeLogic (DateTime creationTime) { 
        _creationTime = creationTime;
    }

    private DateTime _creationTime;
    
    // Returns a collection of NorthwindEmployee objects.
    public ICollection GetCreateTime () {
      ArrayList al = new ArrayList();
      
      // Returns creation time for this example.      
      al.Add("The business object that you are using was created at " + _creationTime);
      
      return al;
    }
  }
}
Imports System.Collections
Imports System.Web.UI
Imports System.Web.UI.WebControls

Namespace Samples.AspNet.VB

  Public Class EmployeeLogic
    
    
    Public Sub New() 
        MyClass.New(DateTime.Now)
    
    End Sub
    
    
    Public Sub New(ByVal creationTime As DateTime) 
        _creationTime = creationTime
    
    End Sub
    
    Private _creationTime As DateTime
    
    
    ' Returns a collection of NorthwindEmployee objects.
    Public Function GetCreateTime() As ICollection 
        Dim al As New ArrayList()
        
        ' Returns creation time for this example.      
        al.Add("The business object that you are using was created at " + _creationTime)
        
        Return al
    
    End Function 'GetCreateTime
  End Class
End Namespace ' Samples.AspNet.VB

Comentarios

Cuando se crea un delegado ObjectDataSourceDisposingEventHandler, se identifica el método que controlará el evento.When you create an ObjectDataSourceDisposingEventHandler delegate, you identify the method that will handle the event. Para asociar el evento al controlador, se debe agregar una instancia del delegado al evento.To associate the event with your event handler, add an instance of the delegate to the event. Siempre que se produce el evento, se llama a su controlador, a menos que se quite el delegado.The event handler is called whenever the event occurs, unless you remove the delegate. Para obtener más información acerca de cómo controlar eventos, vea controlar y provocar eventos.For more information about how to handle events, see Handling and Raising Events.

Métodos de extensión

GetMethodInfo(Delegate)

Obtiene un objeto que representa el método representado por el delegado especificado.Gets an object that represents the method represented by the specified delegate.

Se aplica a

Consulte también