ObjectDataSourceDisposingEventArgs 类

定义

命名空间:: System.Web.UI.WebControls

程序集:: System.Web.dll

重要

一些信息与预发行产品相关，相应产品在发行之前可能会进行重大修改。对于此处提供的信息，Microsoft 不作任何明示或暗示的担保。

为 ObjectDisposing 控件的 ObjectDataSource 事件提供数据。

public ref class ObjectDataSourceDisposingEventArgs : System::ComponentModel::CancelEventArgs

public class ObjectDataSourceDisposingEventArgs : System.ComponentModel.CancelEventArgs

type ObjectDataSourceDisposingEventArgs = class
    inherit CancelEventArgs

Public Class ObjectDataSourceDisposingEventArgs
Inherits CancelEventArgs

继承: Object

EventArgs

CancelEventArgs
ObjectDataSourceDisposingEventArgs

示例

本部分包含两个代码示例。第一个 ObjectDataSource 代码示例演示如何将控件与业务对象和控件配合使用 GridView 来显示信息。第二个代码示例提供第一个代码示例使用的示例中间层业务对象。

下面的代码示例演示如何将 ObjectDataSource 控件与业务对象和控件配合使用 GridView 来显示信息。你可能使用非常昂贵的业务对象， () 为网页执行的每个数据操作创建的时间或资源。使用昂贵对象的一种方法可能是创建一次它的实例，然后缓存它以供后续操作，而不是为每个数据操作创建和销毁它。此示例演示了此模式。可以处理 ObjectCreating 事件以先检查对象的缓存，然后创建一个实例，前提是尚未缓存一个实例。然后，处理 ObjectDisposing 事件以缓存业务对象以供将来使用，而不是销毁它。在此示例中， CancelEventArgs.Cancel 对象的属性 ObjectDataSourceDisposingEventArgs 设置为 true，以指示 ObjectDataSource 不调用 Dispose 实例上的方法。

<%@ 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>

下面的代码示例提供了前面的代码示例使用的示例中间层业务对象。代码示例由类定义 EmployeeLogic 的基本业务对象组成，该类是维护状态并封装业务逻辑的类。对于完整的工作示例，必须将此代码编译为库，然后从 ASP 页使用这些类。

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

注解

在执行ObjectDataSourceDisposingEventArgs使用ObjectDataSource控件和业务对象的任何数据操作之后，但在销毁业务对象之前，在方法中使用 OnObjectDisposing 类来提供对业务对象实例的访问。使用 ObjectInstance 属性访问业务对象。通过添加委托来处理 ObjectDisposing 事件，可以访问业务对象的任何公开成员，以执行任何最终工作或清理。

OnObjectDisposing如果执行数据操作的方法是方法static，则控件不会调用 ObjectDataSource 该方法。当方法为静态时，不会创建任何业务对象实例。

控件 ObjectDataSource 公开了许多事件，你可以在其生命周期的不同时间处理基础业务对象。下表列出了事件以及关联的 EventArgs 类和事件处理程序委托。

事件	EventArgs	EventHandler
ObjectCreating. 紧接在创建业务对象的实例之前发生。	ObjectDataSourceEventArgs	ObjectDataSourceObjectEventHandler
ObjectCreated. 在创建业务对象的实例后立即发生。	ObjectDataSourceEventArgs	ObjectDataSourceObjectEventHandler
Selecting. 在检索数据之前发生。	ObjectDataSourceSelectingEventArgs	ObjectDataSourceSelectingEventHandler
Inserting、 Updating和 Deleting。在执行插入、更新或删除操作之前发生。	ObjectDataSourceMethodEventArgs	ObjectDataSourceMethodEventHandler
Selected 在检索数据后发生。	ObjectDataSourceStatusEventArgs	ObjectDataSourceStatusEventHandler
Inserted、 Updated和 Deleted。在完成插入、更新或删除操作后发生。	ObjectDataSourceStatusEventArgs	ObjectDataSourceStatusEventHandler
ObjectDisposing. 在销毁业务对象之前发生。	ObjectDataSourceDisposingEventArgs	ObjectDataSourceDisposingEventHandler

构造函数

ObjectDataSourceDisposingEventArgs(Object)

使用指定的对象初始化 ObjectDataSourceDisposingEventArgs 类的新实例。

属性

Cancel	获取或设置指示是否应取消事件的值。 (继承自 CancelEventArgs)
ObjectInstance	获取一个对象，该对象表示 ObjectDataSource 控件用来执行数据操作的业务对象。

方法

Equals(Object)	确定指定对象是否等于当前对象。 (继承自 Object)
GetHashCode()	作为默认哈希函数。 (继承自 Object)
GetType()	获取当前实例的 Type。 (继承自 Object)
MemberwiseClone()	创建当前 Object 的浅表副本。 (继承自 Object)
ToString()	返回表示当前对象的字符串。 (继承自 Object)

适用于

另请参阅

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