ObjectDataSource.ObjectDisposing 事件

參考

定義

命名空間:: System.Web.UI.WebControls

組件:: System.Web.dll

重要

部分資訊涉及發行前產品，在發行之前可能會有大幅修改。 Microsoft 對此處提供的資訊，不做任何明確或隱含的瑕疵擔保。

在捨棄 TypeName 屬性識別的物件之前發生。

public:
 event System::Web::UI::WebControls::ObjectDataSourceDisposingEventHandler ^ ObjectDisposing;

public event System.Web.UI.WebControls.ObjectDataSourceDisposingEventHandler ObjectDisposing;

member this.ObjectDisposing : System.Web.UI.WebControls.ObjectDataSourceDisposingEventHandler

Public Custom Event ObjectDisposing As ObjectDataSourceDisposingEventHandler

事件類型

ObjectDataSourceDisposingEventHandler

範例

本節包含兩個程式碼範例。第一個程式碼範例示範如何使用 ObjectDataSource 物件搭配商務物件和 GridView 控制項來顯示資訊。第二個程式碼範例提供第一個程式碼範例中使用的仲介層商務物件。

下列程式碼範例示範如何使用 ObjectDataSource 控制項搭配商務物件和 GridView 控制項來顯示資訊。您可以使用商務物件，針對網頁執行的每個資料作業，建立 (的時間或資源) 非常昂貴。使用昂貴物件的其中一種方式可能是建立一次實例，然後快取它以進行後續作業，而不是針對每個資料作業建立和終結它。此範例示範此模式。您可以先處理 ObjectCreating 事件來檢查物件的快取，而且只有在尚未快取物件時，才建立它的實例。然後，處理 ObjectDisposing 事件來快取商務物件以供日後使用，而不是終結它。在此程式碼範例中 CancelEventArgs.Cancel ObjectDataSourceDisposingEventArgs ，物件的屬性會設定為 true ，以指示 ObjectDataSource 不要在物件上呼叫 Dispose 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>

下列程式碼範例提供上述程式碼範例所使用的中介層商務物件。程式碼範例是由類別所 EmployeeLogic 定義的基本商務物件所組成，這是封裝商務邏輯的具狀態類別。如需完整的工作範例，您必須將此程式碼編譯為程式庫，並從 ASP.NET 網頁 (.aspx 檔案) 使用這些類別。

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

下列範例示範如何在搭配 ObjectDataSource 使用具有 LINQ to SQL 類別的控制項時處理 ObjectDisposing 事件。

Public Sub ExampleObjectDisposing(ByVal sender As Object, _
        ByVal e As ObjectDataSourceDisposingEventArgs)
    e.Cancel = True
End Sub

public void ExampleObjectDisposing(object sender,
        ObjectDataSourceDisposingEventArgs e)
{
    e.Cancel = true;
}

備註

在 ObjectDisposing 捨棄商務物件的實例之前，一律會引發事件。如果商務物件實作 IDisposable 介面， Dispose 則會在引發這個事件之後呼叫方法。

ObjectDisposing處理事件，以在物件、設定屬性或執行物件特有的清除作業之前，呼叫物件上的其他方法。物件的參考是由 ObjectInstance 物件所公開 ObjectDataSourceEventArgs 的屬性所存取。

當您使用 ObjectDataSource 控制項搭配LINQ to SQL類別時，您必須取消在事件的處理常式 ObjectDisposing 中處置資料內容類別別。此步驟是必要的，因為LINQ to SQL支援延後執行，而 ObjectDataSource 控制項則會嘗試在選取作業之後處置資料內容。

如需如何處理事件的詳細資訊，請參閱處理和引發事件。

適用於

ObjectDataSource.ObjectDisposing 事件

定義

事件類型

範例

備註

適用於

另請參閱

意見反應

其他資源