IDisposable Interface

Définition

public interface class IDisposable

public interface IDisposable

[System.Runtime.InteropServices.ComVisible(true)]
public interface IDisposable

type IDisposable = interface

[<System.Runtime.InteropServices.ComVisible(true)>]
type IDisposable = interface

Public Interface IDisposable

Dérivé

DbLinq.Util.BaseLock

Microsoft.Build.Debugging.DebuggerManager.IslandThread

Microsoft.Build.Evaluation.ProjectCollection

Microsoft.Build.Execution.BuildManager

Microsoft.Extensions.Caching.Memory.ICacheEntry

Plus…

Attributs

ComVisibleAttribute

Exemples

L’exemple suivant montre comment créer une classe de ressources qui implémente l' IDisposable interface.The following example demonstrates how to create a resource class that implements the IDisposable interface.

#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

L’utilisation principale de cette interface est de libérer des ressources non managées.The primary use of this interface is to release unmanaged resources. Le « garbage collector » libère automatiquement la mémoire allouée à un objet managé lorsque cet objet n’est plus utilisé.The garbage collector automatically releases the memory allocated to a managed object when that object is no longer used. Toutefois, il n’est pas possible de prédire à quel moment garbage collection se produira.However, it is not possible to predict when garbage collection will occur. En outre, le garbage collector n’a aucune connaissance des ressources non managées telles que les handles de fenêtre ou les fichiers et flux ouverts.Furthermore, the garbage collector has no knowledge of unmanaged resources such as window handles, or open files and streams.

Utilisez la Dispose méthode de cette interface pour libérer explicitement des ressources non managées conjointement avec le garbage collector.Use the Dispose method of this interface to explicitly release unmanaged resources in conjunction with the garbage collector. Le consommateur d’un objet peut appeler cette méthode lorsque l’objet n’est plus nécessaire.The consumer of an object can call this method when the object is no longer needed.

Étant donné que l' IDisposable.Dispose implémentation est appelée par le consommateur d’un type lorsque les ressources détenues par une instance ne sont plus nécessaires, vous devez encapsuler l’objet managé dans un SafeHandle (l’alternative recommandée), ou vous devez substituer Object.Finalize pour libérer des ressources non managées dans l’événement que le consommateur oublie d’appeler Dispose .Because the IDisposable.Dispose implementation is called by the consumer of a type when the resources owned by an instance are no longer needed, you should either wrap the managed object in a SafeHandle (the recommended alternative), or you should override Object.Finalize to free unmanaged resources in the event that the consumer forgets to call Dispose.

Pour une présentation détaillée de l’utilisation de cette interface et de la Object.Finalize méthode, consultez les rubriques nettoyage de la mémoire et implémentation d’une méthode dispose .For a detailed discussion about how this interface and the Object.Finalize method are used, see the Garbage Collection and Implementing a Dispose Method topics.

Utilisation d’un objet qui implémente IDisposableUsing an object that implements IDisposable

Si votre application utilise simplement un objet qui implémente l' IDisposable interface, vous devez appeler l’implémentation de l’objet une IDisposable.Dispose fois que vous avez fini de l’utiliser.If your app simply uses an object that implements the IDisposable interface, you should call the object's IDisposable.Dispose implementation when you are finished using it. En fonction de votre langage de programmation, vous pouvez procéder de deux manières :Depending on your programming language, you can do this in one of two ways:

• En utilisant une construction de langage telle que l' using instruction en C# et Visual Basic.By using a language construct such as the using statement in C# and Visual Basic.

• En encapsulant l’appel à l' IDisposable.Dispose implémentation dans un try / finally bloc.By wrapping the call to the IDisposable.Dispose implementation in a try/finally block.

Instruction C# et Visual Basic usingThe C# and Visual Basic Using statement

Si votre langage prend en charge une construction telle que l’instruction using en C# et l’instruction using dans Visual Basic, vous pouvez l’utiliser au lieu d’appeler explicitement IDisposable.Dispose .If your language supports a construct such as the using statement in C# and the Using statement in Visual Basic, you can use it instead of explicitly calling IDisposable.Dispose yourself. L’exemple suivant utilise cette approche pour définir une WordCount classe qui conserve les informations relatives à un fichier et le nombre de mots qu’il contient.The following example uses this approach in defining a WordCount class that preserves information about a file and the number of words in it.

using System;
using System.IO;
using System.Text.RegularExpressions;

public class WordCount
{
   private String filename = String.Empty;
   private int nWords = 0;
   private String pattern = @"\b\w+\b";

   public WordCount(string filename)
   {
      if (! File.Exists(filename))
         throw new FileNotFoundException("The file does not exist.");

      this.filename = filename;
      string txt = String.Empty;
      using (StreamReader sr = new StreamReader(filename)) {
         txt = sr.ReadToEnd();
      }
      nWords = Regex.Matches(txt, pattern).Count;
   }

   public string FullName
   { get { return filename; } }

   public string Name
   { get { return Path.GetFileName(filename); } }

   public int Count
   { get { return nWords; } }
}

Imports System.IO
Imports System.Text.RegularExpressions

Public Class WordCount
   Private filename As String
   Private nWords As Integer
   Private pattern As String = "\b\w+\b" 

   Public Sub New(filename As String)
      If Not File.Exists(filename) Then
         Throw New FileNotFoundException("The file does not exist.")
      End If   
      
      Me.filename = filename
      Dim txt As String = String.Empty
      Using sr As New StreamReader(filename)
         txt = sr.ReadToEnd()
      End Using
      nWords = Regex.Matches(txt, pattern).Count
   End Sub
   
   Public ReadOnly Property FullName As String
      Get
         Return filename
      End Get   
   End Property
   
   Public ReadOnly Property Name As String
      Get
         Return Path.GetFileName(filename)
      End Get   
   End Property
   
   Public ReadOnly Property Count As Integer
      Get
         Return nWords
      End Get
   End Property
End Class

L' using instruction est en fait une pratique syntaxique.The using statement is actually a syntactic convenience. Au moment de la compilation, le compilateur de langage implémente le langage intermédiaire (il) pour un try / finally bloc.At compile time, the language compiler implements the intermediate language (IL) for a try/finally block.

Pour plus d’informations sur l' using instruction, consultez les rubriques instruction using ou instruction using .For more information about the using statement, see the Using Statement or using Statement topics.

Bloc try/finallyThe Try/Finally block

Si votre langage de programmation ne prend pas en charge une construction telle que l' using instruction en C# ou Visual Basic, ou si vous préférez ne pas l’utiliser, vous pouvez appeler l' IDisposable.Dispose implémentation à partir du finally bloc d’une try / finally instruction.If your programming language does not support a construct like the using statement in C# or Visual Basic, or if you prefer not to use it, you can call the IDisposable.Dispose implementation from the finally block of a try/finally statement. L’exemple suivant remplace le using bloc dans l’exemple précédent par un try / finally bloc.The following example replaces the using block in the previous example with a try/finally block.

using System;
using System.IO;
using System.Text.RegularExpressions;

public class WordCount
{
   private String filename = String.Empty;
   private int nWords = 0;
   private String pattern = @"\b\w+\b";

   public WordCount(string filename)
   {
      if (! File.Exists(filename))
         throw new FileNotFoundException("The file does not exist.");

      this.filename = filename;
      string txt = String.Empty;
      StreamReader sr = null;
      try {
         sr = new StreamReader(filename);
         txt = sr.ReadToEnd();
      }
      finally {
         if (sr != null) sr.Dispose();
      }
      nWords = Regex.Matches(txt, pattern).Count;
   }

   public string FullName
   { get { return filename; } }

   public string Name
   { get { return Path.GetFileName(filename); } }

   public int Count
   { get { return nWords; } }
}

Imports System.IO
Imports System.Text.RegularExpressions

Public Class WordCount
   Private filename As String
   Private nWords As Integer
   Private pattern As String = "\b\w+\b" 

   Public Sub New(filename As String)
      If Not File.Exists(filename) Then
         Throw New FileNotFoundException("The file does not exist.")
      End If   
      
      Me.filename = filename
      Dim txt As String = String.Empty
      Dim sr As StreamReader = Nothing
      Try
         sr = New StreamReader(filename)
         txt = sr.ReadToEnd()
      Finally
         If sr IsNot Nothing Then sr.Dispose() 
      End Try
      nWords = Regex.Matches(txt, pattern).Count
   End Sub
   
   Public ReadOnly Property FullName As String
      Get
         Return filename
      End Get   
   End Property
   
   Public ReadOnly Property Name As String
      Get
         Return Path.GetFileName(filename)
      End Get   
   End Property
   
   Public ReadOnly Property Count As Integer
      Get
         Return nWords
      End Get
   End Property
End Class

Pour plus d’informations sur le try / finally modèle, consultez try... Catch... Instruction finally, try-finallyou try-finally.For more information about the try/finally pattern, see Try...Catch...Finally Statement, try-finally, or try-finally Statement.

Implémentation de IDisposableImplementing IDisposable

Vous devez implémenter IDisposable uniquement si votre type utilise directement des ressources non managées.You should implement IDisposable only if your type uses unmanaged resources directly. Les consommateurs de votre type peuvent appeler votre IDisposable.Dispose implémentation pour libérer des ressources lorsque l’instance n’est plus nécessaire.The consumers of your type can call your IDisposable.Dispose implementation to free resources when the instance is no longer needed. Pour gérer les cas dans lesquels ils ne parviennent pas à appeler Dispose , vous devez utiliser une classe dérivée de SafeHandle pour encapsuler les ressources non managées, ou vous devez substituer la Object.Finalize méthode pour un type référence.To handle cases in which they fail to call Dispose, you should either use a class derived from SafeHandle to wrap the unmanaged resources, or you should override the Object.Finalize method for a reference type. Dans les deux cas, vous utilisez la Dispose méthode pour effectuer le nettoyage nécessaire après avoir utilisé les ressources non managées, telles que la libération, le lancement ou la réinitialisation des ressources non managées.In either case, you use the Dispose method to perform whatever cleanup is necessary after using the unmanaged resources, such as freeing, releasing, or resetting the unmanaged resources.

IDisposable et la hiérarchie d’héritageIDisposable and the inheritance hierarchy

Une classe de base avec des sous-classes qui doivent être jetables doit implémenter IDisposable comme suit.A base class with subclasses that should be disposable must implement IDisposable as follows. Vous devez utiliser ce modèle chaque fois que vous implémentez IDisposable sur un type qui n’est pas sealed ( NotInheritable dans Visual Basic).You should use this pattern whenever you implement IDisposable on any type that isn't sealed (NotInheritable in Visual Basic).

• Il doit fournir une méthode publique, non virtuelle Dispose() et une méthode virtuelle protégée Dispose(Boolean disposing) .It should provide one public, non-virtual Dispose() method and a protected virtual Dispose(Boolean disposing) method.

• La Dispose() méthode doit appeler Dispose(true) et doit supprimer la finalisation des performances.The Dispose() method must call Dispose(true) and should suppress finalization for performance.

• Le type de base ne doit pas inclure de finaliseurs.The base type should not include any finalizers.

Le fragment de code suivant reflète le modèle de suppression pour les classes de base.The following code fragment reflects the dispose pattern for base classes. Elle suppose que votre type ne se substitue pas à la Object.Finalize méthode.It assumes that your type does not override the Object.Finalize method.

using Microsoft.Win32.SafeHandles;
using System;
using System.Runtime.InteropServices;

class BaseClass : IDisposable
{
   // Flag: Has Dispose already been called?
   bool disposed = false;
   // Instantiate a SafeHandle instance.
   SafeHandle handle = new SafeFileHandle(IntPtr.Zero, true);

   // Public implementation of Dispose pattern callable by consumers.
   public void Dispose()
   {
      Dispose(true);
      GC.SuppressFinalize(this);
   }

   // Protected implementation of Dispose pattern.
   protected virtual void Dispose(bool disposing)
   {
      if (disposed)
         return;

      if (disposing) {
         handle.Dispose();
         // Free any other managed objects here.
         //
      }

      disposed = true;
   }
}

Imports Microsoft.Win32.SafeHandles
Imports System.Runtime.InteropServices

Class BaseClass : Implements IDisposable
   ' Flag: Has Dispose already been called?
   Dim disposed As Boolean = False
   ' Instantiate a SafeHandle instance.
   Dim handle As SafeHandle = New SafeFileHandle(IntPtr.Zero, True)

   ' Public implementation of Dispose pattern callable by consumers.
   Public Sub Dispose() _
              Implements IDisposable.Dispose
      Dispose(True)
      GC.SuppressFinalize(Me)           
   End Sub
   
   ' Protected implementation of Dispose pattern.
   Protected Overridable Sub Dispose(disposing As Boolean)
      If disposed Then Return
      
      If disposing Then
         handle.Dispose()
         ' Free any other managed objects here.
         '
      End If
      
      disposed = True
   End Sub
End Class

Si vous substituez la Object.Finalize méthode, votre classe doit implémenter le modèle suivant.If you do override the Object.Finalize method, your class should implement the following pattern.

using System;

class BaseClass : IDisposable
{
   // Flag: Has Dispose already been called?
   bool disposed = false;

   // Public implementation of Dispose pattern callable by consumers.
   public void Dispose()
   {
      Dispose(true);
      GC.SuppressFinalize(this);
   }

   // Protected implementation of Dispose pattern.
   protected virtual void Dispose(bool disposing)
   {
      if (disposed)
         return;

      if (disposing) {
         // Free any other managed objects here.
         //
      }

      // Free any unmanaged objects here.
      //
      disposed = true;
   }

   ~BaseClass()
   {
      Dispose(false);
   }
}

Class BaseClass : Implements IDisposable
   ' Flag: Has Dispose already been called?
   Dim disposed As Boolean = False
   
   ' Public implementation of Dispose pattern callable by consumers.
   Public Sub Dispose() _
              Implements IDisposable.Dispose
      Dispose(True)
      GC.SuppressFinalize(Me)           
   End Sub
   
   ' Protected implementation of Dispose pattern.
   Protected Overridable Sub Dispose(disposing As Boolean)
      If disposed Then Return
      
      If disposing Then
         ' Free any other managed objects here.
         '
      End If
      
      ' Free any unmanaged objects here.
      '
      disposed = True
   End Sub

   Protected Overrides Sub Finalize()
      Dispose(False)      
   End Sub
End Class

Les sous-classes doivent implémenter le modèle supprimable comme suit :Subclasses should implement the disposable pattern as follows:

• Elles doivent substituer Dispose(Boolean) et appeler l'implémentation Dispose(Boolean) de la classe de base.They must override Dispose(Boolean) and call the base class Dispose(Boolean) implementation.

• Elles peuvent fournir un finaliseur, si nécessaire.They can provide a finalizer if needed. Le finaliseur doit appeler Dispose(false).The finalizer must call Dispose(false).

Notez que les classes dérivées n’implémentent pas elles-mêmes l' IDisposable interface et n’incluent pas de méthode sans paramètre Dispose .Note that derived classes do not themselves implement the IDisposable interface and do not include a parameterless Dispose method. Elles remplacent uniquement la méthode de la classe de base Dispose(Boolean) .They only override the base class Dispose(Boolean) method.

Le fragment de code suivant reflète le modèle de suppression pour les classes dérivées.The following code fragment reflects the dispose pattern for derived classes. Elle suppose que votre type ne se substitue pas à la Object.Finalize méthode.It assumes that your type does not override the Object.Finalize method.

using Microsoft.Win32.SafeHandles;
using System;
using System.Runtime.InteropServices;

class DerivedClass : BaseClass
{
   // Flag: Has Dispose already been called?
   bool disposed = false;
   // Instantiate a SafeHandle instance.
   SafeHandle handle = new SafeFileHandle(IntPtr.Zero, true);

   // Protected implementation of Dispose pattern.
   protected override void Dispose(bool disposing)
   {
      if (disposed)
         return;

      if (disposing) {
         handle.Dispose();
         // Free any other managed objects here.
         //
      }

      // Free any unmanaged objects here.
      //

      disposed = true;
      // Call base class implementation.
      base.Dispose(disposing);
   }
}

Imports Microsoft.Win32.SafeHandles
Imports System.Runtime.InteropServices

Class DerivedClass : Inherits BaseClass 
   ' Flag: Has Dispose already been called?
   Dim disposed As Boolean = False
   ' Instantiate a SafeHandle instance.
   Dim handle As SafeHandle = New SafeFileHandle(IntPtr.Zero, True)

   ' Protected implementation of Dispose pattern.
   Protected Overrides Sub Dispose(disposing As Boolean)
      If disposed Then Return
      
      If disposing Then
         handle.Dispose()
         ' Free any other managed objects here.
         '
      End If
      
      ' Free any unmanaged objects here.
      '
      disposed = True
      
      ' Call base class implementation.
      MyBase.Dispose(disposing)
   End Sub
End Class

Méthodes

S’applique à

Voir aussi

• SafeFileHandle
• Implémentation d'une méthode DisposeImplementing a Dispose Method