IDisposable.Dispose Méthode

Définition

Exécute les tâches définies par l'application associées à la libération ou à la redéfinition des ressources non managées.Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.

public:
 void Dispose();
public void Dispose ();
abstract member Dispose : unit -> unit
Public Sub Dispose ()

Exemples

L’exemple suivant montre comment vous pouvez implémenter Dispose la méthode.The following example shows how you can implement the Dispose method.

#using <System.dll>
#using <System.Windows.Forms.dll>

using namespace System;
using namespace System::ComponentModel;
using namespace System::Windows::Forms;

// The following example demonstrates how to create a class that 
// implements the IDisposable interface and the IDisposable.Dispose
// method with finalization to clean up unmanaged resources. 
//
public ref class MyResource: public IDisposable
{
private:

   // Pointer to an external unmanaged resource.
   IntPtr handle;

   // A managed resource this class uses.
   Component^ component;

   // Track whether Dispose has been called.
   bool disposed;

public:
   // The class constructor.
   MyResource( IntPtr handle, Component^ component )
   {
      this->handle = handle;
      this->component = component;
      disposed = false;
   }

   // This method is called if the user explicitly disposes of the
   // object (by calling the Dispose method in other managed languages, 
   // or the destructor in C++). The compiler emits as a call to 
   // GC::SuppressFinalize( this ) for you, so there is no need to 
   // call it here.
   ~MyResource() 
   {
      // Dispose of managed resources.
      component->~Component();

      // Call C++ finalizer to clean up unmanaged resources.
      this->!MyResource();

      // Mark the class as disposed. This flag allows you to throw an
      // exception if a disposed object is accessed.
      disposed = true;
   }

   // Use interop to call the method necessary to clean up the 
   // unmanaged resource.
   //
   [System::Runtime::InteropServices::DllImport("Kernel32")]
   static Boolean CloseHandle( IntPtr handle );

   // The C++ finalizer destructor ensures that unmanaged resources get
   // released if the user releases the object without explicitly 
   // disposing of it.
   //
   !MyResource()
   {      
      // Call the appropriate methods to clean up unmanaged 
      // resources here. If disposing is false when Dispose(bool,
      // disposing) is called, only the following code is executed.
      CloseHandle( handle );
      handle = IntPtr::Zero;
   }

};

void main()
{
   // Insert code here to create and use the MyResource object.
   MyResource^ mr = gcnew MyResource((IntPtr) 42, (Component^) gcnew Button());
   mr->~MyResource();
}
using System;
using System.ComponentModel;

// The following example demonstrates how to create
// a resource class that implements the IDisposable interface
// and the IDisposable.Dispose method.

public class DisposeExample
{
    // A base class that implements IDisposable.
    // By implementing IDisposable, you are announcing that
    // instances of this type allocate scarce resources.
    public class MyResource: IDisposable
    {
        // Pointer to an external unmanaged resource.
        private IntPtr handle;
        // Other managed resource this class uses.
        private Component component = new Component();
        // Track whether Dispose has been called.
        private bool disposed = false;

        // The class constructor.
        public MyResource(IntPtr handle)
        {
            this.handle = handle;
        }

        // Implement IDisposable.
        // Do not make this method virtual.
        // A derived class should not be able to override this method.
        public void Dispose()
        {
            Dispose(true);
            // This object will be cleaned up by the Dispose method.
            // Therefore, you should call GC.SupressFinalize to
            // take this object off the finalization queue
            // and prevent finalization code for this object
            // from executing a second time.
            GC.SuppressFinalize(this);
        }

        // Dispose(bool disposing) executes in two distinct scenarios.
        // If disposing equals true, the method has been called directly
        // or indirectly by a user's code. Managed and unmanaged resources
        // can be disposed.
        // If disposing equals false, the method has been called by the
        // runtime from inside the finalizer and you should not reference
        // other objects. Only unmanaged resources can be disposed.
        protected virtual void Dispose(bool disposing)
        {
            // Check to see if Dispose has already been called.
            if(!this.disposed)
            {
                // If disposing equals true, dispose all managed
                // and unmanaged resources.
                if(disposing)
                {
                    // Dispose managed resources.
                    component.Dispose();
                }

                // Call the appropriate methods to clean up
                // unmanaged resources here.
                // If disposing is false,
                // only the following code is executed.
                CloseHandle(handle);
                handle = IntPtr.Zero;

                // Note disposing has been done.
                disposed = true;

            }
        }

        // Use interop to call the method necessary
        // to clean up the unmanaged resource.
        [System.Runtime.InteropServices.DllImport("Kernel32")]
        private extern static Boolean CloseHandle(IntPtr handle);

        // Use C# destructor syntax for finalization code.
        // This destructor will run only if the Dispose method
        // does not get called.
        // It gives your base class the opportunity to finalize.
        // Do not provide destructors in types derived from this class.
        ~MyResource()
        {
            // Do not re-create Dispose clean-up code here.
            // Calling Dispose(false) is optimal in terms of
            // readability and maintainability.
            Dispose(false);
        }
    }
    public static void Main()
    {
        // Insert code here to create
        // and use the MyResource object.
    }
}
Imports System.ComponentModel

' The following example demonstrates how to create
' a resource class that implements the IDisposable interface
' and the IDisposable.Dispose method.
Public Class DisposeExample

   ' A class that implements IDisposable.
   ' By implementing IDisposable, you are announcing that 
   ' instances of this type allocate scarce resources.
   Public Class MyResource
      Implements IDisposable
      ' Pointer to an external unmanaged resource.
      Private handle As IntPtr
      ' Other managed resource this class uses.
      Private component As component
      ' Track whether Dispose has been called.
      Private disposed As Boolean = False

      ' The class constructor.
      Public Sub New(ByVal handle As IntPtr)
         Me.handle = handle
      End Sub

      ' Implement IDisposable.
      ' Do not make this method virtual.
      ' A derived class should not be able to override this method.
      Public Overloads Sub Dispose() Implements IDisposable.Dispose
         Dispose(True)
         ' This object will be cleaned up by the Dispose method.
         ' Therefore, you should call GC.SupressFinalize to
         ' take this object off the finalization queue 
         ' and prevent finalization code for this object
         ' from executing a second time.
         GC.SuppressFinalize(Me)
      End Sub

      ' Dispose(bool disposing) executes in two distinct scenarios.
      ' If disposing equals true, the method has been called directly
      ' or indirectly by a user's code. Managed and unmanaged resources
      ' can be disposed.
      ' If disposing equals false, the method has been called by the 
      ' runtime from inside the finalizer and you should not reference 
      ' other objects. Only unmanaged resources can be disposed.
      Protected Overridable Overloads Sub Dispose(ByVal disposing As Boolean)
         ' Check to see if Dispose has already been called.
         If Not Me.disposed Then
            ' If disposing equals true, dispose all managed 
            ' and unmanaged resources.
            If disposing Then
               ' Dispose managed resources.
               component.Dispose()
            End If

            ' Call the appropriate methods to clean up 
            ' unmanaged resources here.
            ' If disposing is false, 
            ' only the following code is executed.
            CloseHandle(handle)
            handle = IntPtr.Zero

            ' Note disposing has been done.
            disposed = True

         End If
      End Sub

      ' Use interop to call the method necessary  
      ' to clean up the unmanaged resource.
      <System.Runtime.InteropServices.DllImport("Kernel32")> _
      Private Shared Function CloseHandle(ByVal handle As IntPtr) As [Boolean]
      End Function

      ' This finalizer will run only if the Dispose method 
      ' does not get called.
      ' It gives your base class the opportunity to finalize.
      ' Do not provide finalize methods in types derived from this class.
      Protected Overrides Sub Finalize()
         ' Do not re-create Dispose clean-up code here.
         ' Calling Dispose(false) is optimal in terms of
         ' readability and maintainability.
         Dispose(False)
         MyBase.Finalize()
      End Sub
   End Class

   Public Shared Sub Main()
      ' Insert code here to create
      ' and use the MyResource object.
   End Sub

End Class

Remarques

Utilisez cette méthode pour fermer ou libérer des ressources non managées telles que les fichiers, les flux et les handles détenus par une instance de la classe qui implémente cette interface.Use this method to close or release unmanaged resources such as files, streams, and handles held by an instance of the class that implements this interface. Par Convention, cette méthode est utilisée pour toutes les tâches associées à la libération de ressources détenues par un objet ou à la préparation d’un objet en vue de sa réutilisation.By convention, this method is used for all tasks associated with freeing resources held by an object, or preparing an object for reuse.

Avertissement

Si vous utilisez une classe qui implémente l' IDisposable interface, vous devez appeler son Dispose implémentation lorsque vous avez fini d’utiliser la classe.If you are using a class that implements the IDisposable interface, you should call its Dispose implementation when you are finished using the class. Pour plus d’informations, consultez la section «utilisation d’un objet qui implémente IDisposable» IDisposable dans la rubrique.For more information, see the "Using an object that implements IDisposable" section in the IDisposable topic.

Lors de l’implémentation de cette méthode, assurez-vous que toutes les ressources détenues sont libérées en propageant l’appel via la hiérarchie de relation contenant-contenu.When implementing this method, ensure that all held resources are freed by propagating the call through the containment hierarchy. Par exemple, si un objet A alloue un objet b, et que l’objet b alloue un objet C, l’implémentation de Dispose a doit appeler Dispose sur B, qui doit à son tour Dispose être appelé sur C.For example, if an object A allocates an object B, and object B allocates an object C, then A's Dispose implementation must call Dispose on B, which must in turn call Dispose on C.

Important

Le C++ compilateur prend en charge la suppression déterministe de ressources et n’autorise pas l' Dispose implémentation directe de la méthode.The C++ compiler supports deterministic disposal of resources and does not allow direct implementation of the Dispose method.

Un objet doit également appeler la Dispose méthode de sa classe de base si la classe de base IDisposableimplémente.An object must also call the Dispose method of its base class if the base class implements IDisposable. Pour plus d’informations sur IDisposable l’implémentation de sur une classe de base et ses sous-classes, consultez la section «IDisposable et la hiérarchie IDisposable d’héritage» dans la rubrique.For more information about implementing IDisposable on a base class and its subclasses, see the "IDisposable and the inheritance hierarchy" section in the IDisposable topic.

Si la méthode d' Dispose un objet est appelée plusieurs fois, l’objet doit ignorer tous les appels après le premier.If an object's Dispose method is called more than once, the object must ignore all calls after the first one. L’objet ne doit pas lever d’exception si Dispose sa méthode est appelée plusieurs fois.The object must not throw an exception if its Dispose method is called multiple times. Les méthodes d’instance Dispose autres que peuvent ObjectDisposedException lever une exception lorsque des ressources sont déjà supprimées.Instance methods other than Dispose can throw an ObjectDisposedException when resources are already disposed.

Les utilisateurs peuvent s’attendre à ce qu’un type de ressource utilise une convention particulière pour indiquer un État alloué et un État libéré.Users might expect a resource type to use a particular convention to denote an allocated state versus a freed state. Par exemple, les classes de flux, qui sont généralement considérées comme étant ouvertes ou fermées.An example of this is stream classes, which are traditionally thought of as open or closed. L’implémenteur d’une classe qui a une telle convention peut choisir d’implémenter une méthode publique avec un nom personnalisé, tel Closeque, qui appelle Dispose la méthode.The implementer of a class that has such a convention might choose to implement a public method with a customized name, such as Close, that calls the Dispose method.

Étant donné Dispose que la méthode doit être appelée explicitement, il y a toujours un danger que les ressources non managées ne seront pas libérées, car le consommateur d’un objet Dispose ne parvient pas à appeler sa méthode.Because the Dispose method must be called explicitly, there is always a danger that the unmanaged resources will not be released, because the consumer of an object fails to call its Dispose method. Il existe deux façons d’éviter ceci:There are two ways to avoid this:

  • Encapsulez la ressource managée dans un System.Runtime.InteropServices.SafeHandleobjet dérivé de.Wrap the managed resource in an object derived from System.Runtime.InteropServices.SafeHandle. Votre Dispose implémentation appelle ensuite la Dispose méthode des System.Runtime.InteropServices.SafeHandle instances.Your Dispose implementation then calls the Dispose method of the System.Runtime.InteropServices.SafeHandle instances. Pour plus d’informations, consultez la section «alternative de SafeHandle» Object.Finalize dans la rubrique.For more information, see "The SafeHandle alternative" section in the Object.Finalize topic.

  • Implémentez un finaliseur pour libérer des Dispose ressources lorsque n’est pas appelé.Implement a finalizer to free resources when Dispose is not called. Par défaut, le garbage collector appelle automatiquement le finaliseur d’un objet avant de récupérer sa mémoire.By default, the garbage collector automatically calls an object's finalizer before reclaiming its memory. Toutefois, si la Dispose méthode a été appelée, il est généralement inutile que le garbage collector appelle le finaliseur de l’objet supprimé.However, if the Dispose method has been called, it is typically unnecessary for the garbage collector to call the disposed object's finalizer. Pour empêcher la finalisation automatique Dispose , les implémentations peuvent GC.SuppressFinalize appeler la méthode.To prevent automatic finalization, Dispose implementations can call the GC.SuppressFinalize method.

Lorsque vous utilisez un objet qui accède à des ressources non managées, comme un StreamWriter, il est recommandé de créer l’instance avec une using instruction.When you use an object that accesses unmanaged resources, such as a StreamWriter, a good practice is to create the instance with a using statement. L' using instruction ferme automatiquement le flux et appelle Dispose sur l’objet lorsque le code qui l’utilise est terminé.The using statement automatically closes the stream and calls Dispose on the object when the code that is using it has completed. Pour obtenir un exemple, consultez StreamWriter la classe.For an example, see the StreamWriter class.

S’applique à

Voir aussi