ObjectDataSource.ObjectCreating ObjectDataSource.ObjectCreating ObjectDataSource.ObjectCreating ObjectDataSource.ObjectCreating Event

정의

TypeName 속성으로 식별되는 개체가 만들어지기 전에 발생합니다.Occurs before the object that is identified by the TypeName property is created.

public:
 event System::Web::UI::WebControls::ObjectDataSourceObjectEventHandler ^ ObjectCreating;
public event System.Web.UI.WebControls.ObjectDataSourceObjectEventHandler ObjectCreating;
member this.ObjectCreating : System.Web.UI.WebControls.ObjectDataSourceObjectEventHandler 
Public Custom Event ObjectCreating As ObjectDataSourceObjectEventHandler 

예제

이 섹션에는 두 코드 예제가 있습니다.This section contains two code examples. 첫 번째 코드 예제에 사용 하는 방법을 보여 줍니다.는 ObjectDataSource 비즈니스 개체를 사용 하 여 개체 및 GridView 정보를 표시 하는 컨트롤입니다.The first code example demonstrates how to use an ObjectDataSource object with a business object and a GridView control to display information. 두 번째 코드 예제에서는 첫 번째 코드 예제에 사용 되는 중간 계층 비즈니스 개체를 제공 합니다.The second code example provides the middle-tier business object that is used in the first code example.

다음 코드 예제에 사용 하는 방법을 보여 줍니다.는 ObjectDataSource 비즈니스 개체를 사용 하 여 컨트롤 및 GridView 정보를 표시 하는 컨트롤입니다.The following code example demonstrates how to use an ObjectDataSource control with a business object and a GridView control to display information. 웹 페이지에서 수행 하는 모든 데이터 작업에 대 한 만들기 (시간 또는 리소스) 측면에서 비용이 많이 하는 비즈니스 개체를 사용 하 여 작업할 수 있습니다.You might work with a business object that is very expensive to create (in terms of time or resources) for every data operation your Web page performs. 비용이 많이 드는 개체를 사용 하는 한 가지 방법은 해당 인스턴스를 한 번 만들어를 만들고 모든 데이터 작업에 대 한 제거 하는 대신 다음 작업에 캐시 될 수 있습니다.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.

참고

프로덕션 애플리케이션에서는 여러 요청이 동시에 동일한 인스턴스를 사용 하 여 생길 수 있습니다.In a production application, multiple requests might end up simultaneously using the same instance. 따라서 개체는 스레드로부터 안전한 방식으로 구현 해야 합니다.Therefore, the object needs to be implemented in a thread-safe manner.

이 코드 예제에서는이 패턴을 보여 줍니다.This code example demonstrates this pattern. 처리할 수 있습니다는 ObjectCreating 이벤트 개체에 대 한 캐시를 먼저 확인 하 고 이미 캐시 되지 않으면만 개체의 인스턴스를 만듭니다.You can handle the ObjectCreating event to check the cache for an object first, and only create an instance of the object, if one is not already cached. 그런 다음 처리를 ObjectDisposing 이벤트를 제거 하는 대신 나중에 사용할 비즈니스 개체를 캐시 합니다.Then, handle the ObjectDisposing event to cache the business object for future use, instead of destroying it. 이 코드 예제에서는 CancelEventArgs.Cancel 의 속성을 ObjectDataSourceDisposingEventArgs 개체로 설정 됩니다 true 보내기 위해는 ObjectDataSource 를 호출 하지 않도록 Dispose 개체의 메서드를.In this code example, the CancelEventArgs.Cancel property of the ObjectDataSourceDisposingEventArgs object is set to true to direct the ObjectDataSource to not call Dispose method on the object.

<%@ 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>

다음 코드 예제에서는 앞의 코드 예제를 사용 하는 예제에서는 중간 계층 비즈니스 개체를 제공 합니다.The following code example provides the example middle-tier business object that the preceding code example uses. 정의한 기본 비즈니스 개체의 코드 예제는는 EmployeeLogic 비즈니스 논리를 캡슐화 하는 상태 저장 클래스 클래스.The code example consists of a basic business object, defined by the EmployeeLogic class, which is a stateful class that encapsulates business logic. 전체 작업 예제를 보려면이 코드를 라이브러리로 컴파일하고 ASP.NET 페이지 (.aspx 파일)에서 이러한 클래스를 사용 합니다.For a complete working example, you must compile this code as a library and use these classes from an ASP.NET page (.aspx file).

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

설명

경우 데이터 작업을 수행 하려면 식별 되는 메서드는 static (Shared Visual Basic에서), ObjectCreatingObjectCreated 이벤트는 발생 하지 않습니다.If the method that is identified to perform the data operation is static (Shared in Visual Basic), the ObjectCreating and ObjectCreated events are never raised.

컨트롤 ObjectDataSource 은 비즈니스 개체의 매개 변수가 없는 생성자를 자동으로 호출 하 여 리플렉션을 사용 하 여 인스턴스를 만듭니다.The ObjectDataSource control automatically calls the parameterless constructor of a business object to create an instance of it using reflection. 처리를 ObjectCreating 이벤트를 명시적으로 다른 생성자를 호출 하 고 결과 개체의 인스턴스를 설정 합니다 ObjectInstance 속성은 연결 된 ObjectDataSourceEventArgs 개체입니다.Handle the ObjectCreating event to explicitly call another constructor, and set the instance of the object that results to the ObjectInstance property of the associated ObjectDataSourceEventArgs object.

이벤트를 처리 하는 방법에 대 한 자세한 내용은 참조 하세요. 이벤트 처리 및 발생합니다.For more information about how to handle events, see Handling and Raising Events.

적용 대상

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