IDisposable IDisposable IDisposable IDisposable Interface

Definizione

public interface class IDisposable

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

type IDisposable = interface

Public Interface IDisposable

Derivato

BaseLockBaseLockBaseLockBaseLock

DebuggerManager.IslandThreadDebuggerManager.IslandThreadDebuggerManager.IslandThreadDebuggerManager.IslandThread

ProjectCollectionProjectCollectionProjectCollectionProjectCollection

BuildManagerBuildManagerBuildManagerBuildManager

BaseDataEnvironmentBaseDataEnvironmentBaseDataEnvironmentBaseDataEnvironment

Altro…

Attributi

ComVisibleAttribute

Esempi

Nell'esempio seguente viene illustrato come creare una classe di risorse che implementa il IDisposable interfaccia.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
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

Commenti

L'uso primario di questa interfaccia è per rilasciare le risorse non gestite.The primary use of this interface is to release unmanaged resources. Il garbage collector rilascia automaticamente la memoria allocata a un oggetto gestito quando tale oggetto non viene più utilizzata.The garbage collector automatically releases the memory allocated to a managed object when that object is no longer used. Non è tuttavia possibile prevedere quando verrà eseguita la garbage collection.However, it is not possible to predict when garbage collection will occur. Inoltre, il garbage collector non è a conoscenza delle risorse non gestite, ad esempio gli handle di finestra o aprire file e flussi.Furthermore, the garbage collector has no knowledge of unmanaged resources such as window handles, or open files and streams.

Usare il Dispose metodo dell'interfaccia rilasciare in modo esplicito le risorse non gestite in combinazione con il garbage collector.Use the Dispose method of this interface to explicitly release unmanaged resources in conjunction with the garbage collector. Il consumer di un oggetto può chiamare questo metodo quando l'oggetto non è più necessario.The consumer of an object can call this method when the object is no longer needed.

Poiché il IDisposable.Dispose implementazione viene chiamata dal consumer di un tipo quando le risorse di proprietà da un'istanza non sono più necessari, è necessario includere sia l'oggetto gestito in un SafeHandle (l'alternativa consigliata) o eseguire l'override Object.Finalizeper liberare le risorse non gestite nel caso in cui il consumer ometta di chiamare 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.

Per informazioni dettagliate su come questa interfaccia e il Object.Finalize metodo, vedere la Garbage Collection e che implementa un metodo Dispose argomenti.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.

Uso di un oggetto che implementa IDisposableUsing an object that implements IDisposable

Se l'app Usa semplicemente un oggetto che implementa il IDisposable interfaccia, è necessario chiamare l'oggetto IDisposable.Dispose implementazione quando si è finito di usarlo.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. A seconda del linguaggio di programmazione, è possibile procedere in uno dei due modi:Depending on your programming language, you can do this in one of two ways:

• Usando un linguaggio di costruire, ad esempio il using istruzione in c# e Visual Basic.By using a language construct such as the using statement in C# and Visual Basic.

• Eseguendo il wrapping della chiamata ai IDisposable.Dispose implementazione in una try / finally blocco.By wrapping the call to the IDisposable.Dispose implementation in a try/finally block.

L'istruzione c# e Visual Basic usandoThe C# and Visual Basic Using statement

Se il linguaggio supporta un costrutto, ad esempio la usando istruzione in c# e il Using istruzione in Visual Basic, è possibile usarlo invece di chiamare in modo esplicito IDisposable.Dispose manualmente.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'esempio seguente usa questo approccio nella definizione di un WordCount classe che mantiene le informazioni su un file e il numero di parole in esso.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

Il using istruzione è effettivamente una convenzione sintattica.The using statement is actually a syntactic convenience. In fase di compilazione, il compilatore di linguaggio implementa il linguaggio intermedio (IL) per un try / finally blocco.At compile time, the language compiler implements the intermediate language (IL) for a try/finally block.

Per altre informazioni sul using istruzione, vedere la istruzione Using o istruzione using argomenti.For more information about the using statement, see the Using Statement or using Statement topics.

Il blocco Try/FinallyThe Try/Finally block

Se il linguaggio di programmazione non supporta un costrutto, ad esempio la using istruzione in c# o Visual Basic, oppure se non si vuole usarlo, è possibile chiamare il IDisposable.Dispose implementazione dal finally blocco di un try / finally istruzione.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. Nell'esempio seguente sostituisce la using bloccare nell'esempio precedente con un try / finally blocco.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

Per altre informazioni sul try / finally pattern, vedere Try... Catch... Istruzione finally, try-finally, o istruzione try-finally.For more information about the try/finally pattern, see Try...Catch...Finally Statement, try-finally, or try-finally Statement.

Implementazione di IDisposableImplementing IDisposable

È consigliabile implementare IDisposable solo se il tipo Usa direttamente le risorse non gestite.You should implement IDisposable only if your type uses unmanaged resources directly. I consumer del tipo in uso è possono chiamare il IDisposable.Dispose implementazione per liberare risorse quando l'istanza non è più necessario.The consumers of your type can call your IDisposable.Dispose implementation to free resources when the instance is no longer needed. Per gestire i casi in cui questi non riescono a chiamare Dispose, è necessario usare una classe derivata da SafeHandle per eseguire il wrapping di risorse non gestite, o si deve eseguire l'override di Object.Finalize metodo per un tipo riferimento.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. In entrambi i casi, si utilizza il Dispose metodo per eseguire qualsiasi pulizia necessaria dopo aver usato le risorse non gestite, ad esempio liberare, rilasciare o reimpostare le risorse non gestite.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 e la gerarchia di ereditarietàIDisposable and the inheritance hierarchy

Una classe di base con sottoclassi eliminabili deve implementare IDisposable come indicato di seguito.A base class with subclasses that should be disposable must implement IDisposable as follows. È consigliabile usare questo modello ogni volta che si implementa IDisposable su qualsiasi tipo che non sia sealed (NotInheritable in Visual Basic).You should use this pattern whenever you implement IDisposable on any type that isn't sealed (NotInheritable in Visual Basic).

• È necessario fornire una pubblica, non virtuale Dispose() metodo e un protetto virtuale Dispose(Boolean disposing) (metodo).It should provide one public, non-virtual Dispose() method and a protected virtual Dispose(Boolean disposing) method.

• Il Dispose() metodo deve chiamare Dispose(true) e deve eliminare la finalizzazione per le prestazioni.The Dispose() method must call Dispose(true) and should suppress finalization for performance.

• Il tipo di base non deve includere alcun finalizzatore.The base type should not include any finalizers.

Nel seguente frammento di codice riflette il modello dispose per le classi di base.The following code fragment reflects the dispose pattern for base classes. Si presuppone che il tipo non esegue l'override di Object.Finalize (metodo).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

Se si esegue l'override di Object.Finalize metodo, la classe deve implementare il modello seguente.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

Le sottoclassi devono implementare il modello Disposable come segue:Subclasses should implement the disposable pattern as follows:

• È necessario eseguire l'override di Dispose(Boolean) e chiamare l'implementazione Dispose(Boolean) della classe di base.They must override Dispose(Boolean) and call the base class Dispose(Boolean) implementation.

• Possono fornire un finalizzatore, se necessario.They can provide a finalizer if needed. Il finalizzatore deve chiamare Dispose(false).The finalizer must call Dispose(false).

Si noti che le classi derivate non possono implementare il IDisposable dell'interfaccia e non includono un senza parametri Dispose (metodo).Note that derived classes do not themselves implement the IDisposable interface and do not include a parameterless Dispose method. Essi eseguire l'override solo la classe di base Dispose(Boolean) (metodo).They only override the base class Dispose(Boolean) method.

Nel seguente frammento di codice riflette il modello dispose per le classi derivate.The following code fragment reflects the dispose pattern for derived classes. Si presuppone che il tipo non esegue l'override di Object.Finalize (metodo).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

Metodi

Si applica a

Vedi anche

• SafeFileHandle
• Implementazione di un metodo DisposeImplementing a Dispose Method