IDisposable.Dispose Método

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

En el ejemplo siguiente se muestra cómo se puede Dispose implementar el 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.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 y 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 utiliza para todas las tareas asociadas a la liberación de recursos mantenidos por un objeto o para 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 la IDisposable interfaz, debe llamar a su Dispose implementación cuando termine de utilizar la clase.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 "usar un objeto que implementa IDisposable" del 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 los recursos retenidos se liberan propagando 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, la implementación de Dispose un debe llamar Dispose a en B, que a su vez debe llamar Dispose a 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 C++ compilador admite la eliminación determinista de recursos y no permite la Dispose implementación directa del método.The C++ compiler supports deterministic disposal of resources and does not allow direct implementation of the Dispose method.

Un objeto también debe llamar al Dispose método de su clase base si la clase base IDisposableimplementa.An object must also call the Dispose method of its base class if the base class implements IDisposable. Para obtener más información sobre IDisposable la implementación de en una clase base y sus subclases, vea la sección "IDisposable y la jerarquía IDisposable de herencia" del 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 se llama a Dispose un método de un objeto más de una vez, el objeto debe omitir 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 Dispose se llama al método varias veces.The object must not throw an exception if its Dispose method is called multiple times. Los métodos de instancia Dispose distintos de pueden ObjectDisposedException producir una excepción cuando los recursos ya se han desechado.Instance methods other than Dispose can throw an ObjectDisposedException when resources are already disposed.

Los usuarios podrían esperar que un tipo de recurso use una convención determinada para indicar un estado asignado frente a un estado liberado.Users might expect a resource type to use a particular convention to denote an allocated state versus a freed state. Un ejemplo de esto son las clases de flujo, que tradicionalmente se consideran 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 tal convención podría optar por implementar un método público con un nombre personalizado, Closecomo, que llama al 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.

Dado que Dispose se debe llamar al método explícitamente, siempre hay un riesgo de que no se liberen los recursos no administrados, ya que el consumidor de un objeto no Dispose puede llamar a su 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 evitar esto:There are two ways to avoid this:

  • Encapsula 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. A Dispose continuación, la implementación Dispose llama al método System.Runtime.InteropServices.SafeHandle de las instancias de.Your Dispose implementation then calls the Dispose method of the System.Runtime.InteropServices.SafeHandle instances. Para obtener más información, consulte la sección "alternativa de SafeHandle" Object.Finalize del tema.For more information, see "The SafeHandle alternative" section in the Object.Finalize topic.

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

Cuando se usa un objeto que tiene acceso a recursos no administrados, StreamWritercomo, se recomienda crear la instancia con una 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. La using instrucción cierra automáticamente la secuencia y llama Dispose a en el objeto cuando se completa el código que lo está utilizando.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 StreamWriter la clase.For an example, see the StreamWriter class.

Se aplica a

Consulte también: