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

Definition

Führt anwendungsspezifische Aufgaben durch, die mit der Freigabe, der Zurückgabe oder dem Zurücksetzen von nicht verwalteten Ressourcen zusammenhängen.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 ()

Beispiele

Das folgende Beispiel zeigt, wie Sie implementieren die Dispose Methode.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

Hinweise

Verwenden Sie diese Methode, geschlossen oder freigegeben nicht verwaltete Ressourcen wie z. B. Dateien, Streams und Handles frei, die eine Instanz der Klasse, die diese Schnittstelle implementiert.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. Diese Methode wird gemäß der Konvention für alle Aufgaben im Zusammenhang mit der Freigabe ein Objekt reservierten Ressourcen verwendet oder der Vorbereitung der Wiederverwendung eines Objekts.By convention, this method is used for all tasks associated with freeing resources held by an object, or preparing an object for reuse.

Warnung

Wenn Sie eine Klasse verwenden, die implementiert die IDisposable -Schnittstelle, rufen Sie die Dispose Implementierung Sie abschließend mithilfe der Klasse.If you are using a class that implements the IDisposable interface, you should call its Dispose implementation when you are finished using the class. Weitere Informationen finden Sie im Abschnitt "Verwenden ein Objekt, das IDisposable implementiert" in der IDisposable Thema.For more information, see the "Using an object that implements IDisposable" section in the IDisposable topic.

Wenn Sie diese Methode implementieren, stellen Sie sicher, dass alle Ressourcen freigegeben werden reservierten, indem der Aufruf durch die Kapselungshierarchie.When implementing this method, ensure that all held resources are freed by propagating the call through the containment hierarchy. Angenommen, ein Objekt weist ein Objekt B, und Objekt B eines Objekts C, klicken Sie dann ein Dispose Implementierung muss Aufrufen Dispose auf B die aufrufen muss Dispose in 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.

Wichtig

Der C++-Compiler unterstützt die deterministische Verwerfen von Ressourcen und lässt sich nicht auf die direkte Implementierung der der Dispose Methode.The C++ compiler supports deterministic disposal of resources and does not allow direct implementation of the Dispose method.

Ein Objekt muss auch aufrufen, die Dispose Methode ihrer Basisklasse, wenn die Basisklasse implementiert IDisposable.An object must also call the Dispose method of its base class if the base class implements IDisposable. Weitere Informationen zum Implementieren von IDisposable auf eine Basisklasse und ihrer Unterklassen, finden Sie im Abschnitt "" IDisposable "und der Vererbungshierarchie" in der IDisposable Thema.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.

Wenn ein Objekt des Dispose Methode mehr als einmal aufgerufen wird, wird das Objekt muss alle Aufrufe nach der ersten ignoriert.If an object's Dispose method is called more than once, the object must ignore all calls after the first one. Das Objekt muss keine Ausnahme ausgelöst, wenn die Dispose Methode mehrmals aufgerufen wird.The object must not throw an exception if its Dispose method is called multiple times. Instanzmethoden außer Dispose Auslösen einer ObjectDisposedException Wenn Ressourcen bereits freigegeben.Instance methods other than Dispose can throw an ObjectDisposedException when resources are already disposed.

Benutzer erwarten einen Ressourcentyp aus, um eine bestimmte Vereinbarung zu verwenden, um eine zugeordnete Zustand im Vergleich zu einem freigegebenen Zustand zu bezeichnen.Users might expect a resource type to use a particular convention to denote an allocated state versus a freed state. Ein Beispiel hierfür ist die Stream-Klassen, die normalerweise als geöffnet oder geschlossen.An example of this is stream classes, which are traditionally thought of as open or closed. Die Implementierung von einer Klasse mit einer derartigen kann auch eine öffentliche Methode mit einem benutzerdefinierten Namen, z. B. implementiert Close, die Aufrufe der Dispose Methode.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.

Da die Dispose -Methode muss explizit aufgerufen werden, besteht immer die Gefahr, die nicht verwalteten Ressourcen nicht freigegeben werden, da der Consumer eines Objekts aufrufen, um kann die Dispose Methode.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. Es gibt zwei Möglichkeiten, dies zu vermeiden:There are two ways to avoid this:

  • Umschließen Sie die verwaltete Ressource in einem Objekt abgeleitet System.Runtime.InteropServices.SafeHandle.Wrap the managed resource in an object derived from System.Runtime.InteropServices.SafeHandle. Ihre Dispose Implementierung ruft die Dispose Methode der System.Runtime.InteropServices.SafeHandle Instanzen.Your Dispose implementation then calls the Dispose method of the System.Runtime.InteropServices.SafeHandle instances. Weitere Informationen finden Sie im Abschnitt "Die SafeHandle-Alternative" die Object.Finalize Thema.For more information, see "The SafeHandle alternative" section in the Object.Finalize topic.

  • Implementieren Sie einen Finalizer, um Ressourcen freizugeben, wenn Dispose wird nicht aufgerufen.Implement a finalizer to free resources when Dispose is not called. Standardmäßig ruft der Garbage Collector den Finalizer des Objekts automatisch vor der Rückgabe des Speichers.By default, the garbage collector automatically calls an object's finalizer before reclaiming its memory. Aber wenn die Dispose Methode wurde aufgerufen wird, ist es in der Regel nicht erforderlich, für den Garbage Collector freigegeben den Finalizer des Objekts aufrufen.However, if the Dispose method has been called, it is typically unnecessary for the garbage collector to call the disposed object's finalizer. Um zu verhindern, dass automatische Beendigung, Dispose Implementierungen können aufrufen, die GC.SuppressFinalize Methode.To prevent automatic finalization, Dispose implementations can call the GC.SuppressFinalize method.

Ein Objekt, das nicht verwaltete Ressourcen, z. B. zugreift bei Verwendung einer StreamWriter, eine bewährte Methode wird zum Erstellen der Instanz mit einem using Anweisung.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. Die using Anweisung schließt automatisch den Stream und ruft Dispose für das Objekt nach Abschluss der Code, der es verwendet wird.The using statement automatically closes the stream and calls Dispose on the object when the code that is using it has completed. Ein Beispiel finden Sie unter den StreamWriter Klasse.For an example, see the StreamWriter class.

Gilt für:

Siehe auch