IDisposable.Dispose IDisposable.Dispose IDisposable.Dispose IDisposable.Dispose Method

Definición

Realiza tareas definidas por la aplicación asociadas a la liberación o al restablecimiento de recursos no administrados.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 ()

Ejemplos

El ejemplo siguiente muestra cómo puede implementar la Dispose método.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
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

Comentarios

Utilice este método para cerrar o liberar recursos no administrados como archivos, secuencias e identificadores mantenidos por una instancia de la clase que implementa esta interfaz.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. Por convención, este método se usa para todas las tareas asociadas con los recursos mantenidos por un objeto, se liberan o preparar un objeto para su reutilización.By convention, this method is used for all tasks associated with freeing resources held by an object, or preparing an object for reuse.

Advertencia

Si usa una clase que implementa el IDisposable interfaz, debe llamar a su Dispose cuando haya terminado de utilizar la clase de implementación.If you are using a class that implements the IDisposable interface, you should call its Dispose implementation when you are finished using the class. Para obtener más información, vea la sección "Uso de un objeto que implementa IDisposable" en el IDisposable tema.For more information, see the "Using an object that implements IDisposable" section in the IDisposable topic.

Al implementar este método, asegúrese de que todos mantienen se liberan los recursos mediante la propagación de la llamada a través de la jerarquía de contención.When implementing this method, ensure that all held resources are freed by propagating the call through the containment hierarchy. Por ejemplo, si un objeto A asigna un objeto B, y el objeto B asigna un objeto C, a continuación, un Dispose implementación debe llamar a Dispose en B, que debe llamar a su vez Dispose en 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.

Importante

El compilador de C++ admite la eliminación determinista de recursos y no se permite la implementación directa de la Dispose método.The C++ compiler supports deterministic disposal of resources and does not allow direct implementation of the Dispose method.

También debe llamar un objeto la Dispose método de su clase base si la clase base implementa IDisposable.An object must also call the Dispose method of its base class if the base class implements IDisposable. Para obtener más información acerca de cómo implementar IDisposable en una clase base y sus subclases, consulte la sección "IDisposable y la jerarquía de herencia" en el IDisposable tema.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 un objeto Dispose método se llama varias veces, el objeto debe tener en cuenta todas las llamadas posteriores a la primera.If an object's Dispose method is called more than once, the object must ignore all calls after the first one. El objeto no debe producir una excepción si su Dispose método se llama varias veces.The object must not throw an exception if its Dispose method is called multiple times. Métodos de instancia distinto Dispose puede producir un ObjectDisposedException cuando ya se eliminen los recursos.Instance methods other than Dispose can throw an ObjectDisposedException when resources are already disposed.

Los usuarios de esperar un tipo de recurso para usar una convención determinada para indicar un estado de asignación frente a un estado de liberación.Users might expect a resource type to use a particular convention to denote an allocated state versus a freed state. Un ejemplo de esto es que las clases de secuencia, que tradicionalmente se consideran como abiertas o cerradas.An example of this is stream classes, which are traditionally thought of as open or closed. El implementador de una clase que tiene una convención de este tipo puede optar por implementar un método público con un nombre personalizado, como Close, que llama a la Dispose método.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.

Porque el Dispose debe llamar explícitamente al método, siempre hay un riesgo de que los recursos no administrados no se ha liberado, porque el consumidor de un objeto no llama a su Dispose método.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. Hay dos maneras de evitarlo:There are two ways to avoid this:

  • Ajustar el recurso administrado en un objeto derivado de System.Runtime.InteropServices.SafeHandle.Wrap the managed resource in an object derived from System.Runtime.InteropServices.SafeHandle. Su Dispose implementación, a continuación, llama a la Dispose método de la System.Runtime.InteropServices.SafeHandle instancias.Your Dispose implementation then calls the Dispose method of the System.Runtime.InteropServices.SafeHandle instances. Para obtener más información, consulte la sección "La alternativa SafeHandle" en el Object.Finalize tema.For more information, see "The SafeHandle alternative" section in the Object.Finalize topic.

  • Implementar un finalizador para liberar recursos cuando Dispose no se llama.Implement a finalizer to free resources when Dispose is not called. De forma predeterminada, el recolector de elementos no utilizados llama automáticamente a un finalizador del objeto antes de reclamar su memoria.By default, the garbage collector automatically calls an object's finalizer before reclaiming its memory. Sin embargo, si la Dispose ha sido el método llamado, normalmente no es necesario para el recolector de elementos no utilizados llame al finalizador del objeto desechado.However, if the Dispose method has been called, it is typically unnecessary for the garbage collector to call the disposed object's finalizer. Para evitar una finalización automática, Dispose pueden llamar las implementaciones del GC.SuppressFinalize método.To prevent automatic finalization, Dispose implementations can call the GC.SuppressFinalize method.

Cuando se usa un objeto que tiene acceso a los recursos no administrados, como un StreamWriter, es una buena práctica crear la instancia con un using instrucción.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. El using instrucción cierra automáticamente la secuencia y llama a Dispose en el objeto cuando se haya completado el código que lo usa.The using statement automatically closes the stream and calls Dispose on the object when the code that is using it has completed. Para obtener un ejemplo, vea el StreamWriter clase.For an example, see the StreamWriter class.

Se aplica a

Consulte también: