ObjectDataSourceDisposingEventHandler ObjectDataSourceDisposingEventHandler ObjectDataSourceDisposingEventHandler ObjectDataSourceDisposingEventHandler Delegate

定義

ObjectDisposing コントロールの ObjectDataSource イベントを処理するメソッドを表します。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)

パラメーター

sender
Object Object Object Object

イベントのソースである ObjectDataSourceThe source of the event, the ObjectDataSource.

継承
ObjectDataSourceDisposingEventHandlerObjectDataSourceDisposingEventHandlerObjectDataSourceDisposingEventHandlerObjectDataSourceDisposingEventHandler

このセクションには、2 つのコード例が含まれています。This section contains two code examples. 最初のコード例を使用する方法を示します、ObjectDataSourceビジネス オブジェクトを持つコントロールとGridView情報を表示するコントロール。The first code example demonstrates how to use an ObjectDataSource control with a business object and a GridView control to display information. 2 番目のコード例では、最初のコード例を使用する中間層ビジネス オブジェクトの例を提供します。The second code example provides an example middle-tier business object that the first code example uses.

次のコード例は、使用する方法を示します、ObjectDataSourceビジネス オブジェクトを持つコントロールとGridView情報を表示するコントロール。The following code example demonstrates how to use an ObjectDataSource control with a business object and a GridView control to display information. Web ページで実行するすべてのデータ操作を作成する (時間またはリソース) 観点から非常に安価にするビジネス オブジェクトを操作する可能性があります。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. 1 回、そのインスタンスを作成し、残りの操作を作成して、各データ操作を破棄する代わりにキャッシュし、負荷の高いオブジェクトを使用する方法の 1 つがあります。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. この例では、このパターンを示します。This example demonstrates this pattern. 処理することができます、ObjectCreatingイベント オブジェクトは、最初にキャッシュを確認し、1 つが既にキャッシュされていない場合にのみ、インスタンスを作成します。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. 次に、処理、ObjectDisposingイベントを破棄するのではなく、将来使用するためのビジネス オブジェクトをキャッシュします。Then, handle the ObjectDisposing event to cache the business object for future use, instead of destroying it. この例で、CancelEventArgs.Cancelのプロパティ、ObjectDataSourceDisposingEventArgsクラスに設定されているtrue、出力するため、ObjectDataSourceを呼び出してDisposeインスタンスでします。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>

次のコード例では、上記のコード例を使用する中間層ビジネス オブジェクトの例を提供します。The following code example provides an example middle-tier business object that the preceding code example uses. コード例で定義される、基本的なビジネス オブジェクトから成る、EmployeeLogicクラスは、状態を維持し、ビジネス ロジックをカプセル化するクラスです。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. 完全な作業例については、ライブラリとしてこのコードをコンパイルし、ASP ページからこれらのクラスを使用してください。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
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 'New
    
    
    Public Sub New(ByVal creationTime As DateTime) 
        _creationTime = creationTime
    
    End Sub 'New
    
    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 'EmployeeLogic
End Namespace ' Samples.AspNet.VB

注釈

ObjectDataSourceDisposingEventHandler デリゲートを作成する場合は、イベントを処理するメソッドを指定します。When you create an ObjectDataSourceDisposingEventHandler delegate, you identify the method that will handle the event. イベントをイベント ハンドラーに関連付けるには、デリゲートのインスタンスをイベントに追加します。To associate the event with your event handler, add an instance of the delegate to the event. デリゲートを削除しない限り、そのイベントが発生すると常にイベント ハンドラーが呼び出されます。The event handler is called whenever the event occurs, unless you remove the delegate. イベントを処理する方法の詳細については、次を参照してください。処理とイベントの発生します。For more information about how to handle events, see Handling and Raising Events.

拡張メソッド

GetMethodInfo(Delegate) GetMethodInfo(Delegate) GetMethodInfo(Delegate) GetMethodInfo(Delegate)

指定したデリゲートによって表されるメソッドを表すオブジェクトを取得します。Gets an object that represents the method represented by the specified delegate.

適用対象

こちらもご覧ください