IDisposable Интерфейс

Определение

public interface class IDisposable

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

type IDisposable = interface

Public Interface IDisposable

Производный

DbLinq.Util.BaseLock

Microsoft.Build.Debugging.DebuggerManager.IslandThread

Microsoft.Build.Evaluation.ProjectCollection

Microsoft.Build.Execution.BuildManager

Microsoft.Extensions.Caching.Memory.ICacheEntry

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Атрибуты

ComVisibleAttribute

Примеры

В следующем примере показано, как создать класс ресурсов, реализующий интерфейс IDisposable.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

Комментарии

В основном этот интерфейс используется для высвобождения неуправляемых ресурсов.The primary use of this interface is to release unmanaged resources. Сборщик мусора автоматически освобождает память, выделенную управляемому объекту, если этот объект больше не используется.The garbage collector automatically releases the memory allocated to a managed object when that object is no longer used. Однако невозможно предсказать, когда произойдет сборка мусора.However, it is not possible to predict when garbage collection will occur. Более того, сборщик мусора не имеет сведений о неуправляемых ресурсах, таких как дескрипторы окон, или открытых файлах и потоках.Furthermore, the garbage collector has no knowledge of unmanaged resources such as window handles, or open files and streams.

Используйте метод Dispose этого интерфейса, чтобы явным образом освободить неуправляемые ресурсы в сочетании с сборщиком мусора.Use the Dispose method of this interface to explicitly release unmanaged resources in conjunction with the garbage collector. Потребитель объекта может вызвать этот метод, если объект больше не нужен.The consumer of an object can call this method when the object is no longer needed.

Поскольку реализация IDisposable.Dispose вызывается потребителем типа, когда ресурсы, принадлежащие экземпляру, больше не требуются, необходимо либо заключить управляемый объект в SafeHandle (рекомендуемый альтернативный вариант), либо переопределить Object.Finalize для освобождения неуправляемых ресурсов в случае, если потребитель забудет вызвать 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.

Подробное обсуждение использования этого интерфейса и метода Object.Finalize см. в разделах сборка мусора и Реализация метода 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.

Использование объекта, реализующего IDisposableUsing an object that implements IDisposable

Если приложение просто использует объект, реализующий интерфейс IDisposable, необходимо вызвать реализацию IDisposable.Dispose объекта, когда вы завершите его использование.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. В зависимости от языка программирования это можно сделать одним из двух способов:Depending on your programming language, you can do this in one of two ways:

• С помощью языковой конструкции, такой как оператор using в C# и Visual Basic.By using a language construct such as the using statement in C# and Visual Basic.

• Путем заключения вызова к реализации IDisposable.Dispose в блоке try/finally.By wrapping the call to the IDisposable.Dispose implementation in a try/finally block.

Оператор C# и Visual Basic usingThe C# and Visual Basic Using statement

Если ваш язык поддерживает конструкцию, такую как оператор using в C# , и оператор using в Visual Basic, его можно использовать вместо явного вызова 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. В следующем примере этот подход используется при определении WordCount класса, который сохраняет сведения о файле и количестве слов в нем.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

Инструкция using на самом деле является синтаксическим удобством.The using statement is actually a syntactic convenience. Во время компиляции языковой компилятор реализует промежуточный язык (IL) для try/блока finally.At compile time, the language compiler implements the intermediate language (IL) for a try/finally block.

Дополнительные сведения о using инструкции см. в разделах инструкция using или инструкции по использованию .For more information about the using statement, see the Using Statement or using Statement topics.

Блок try/finallyThe Try/Finally block

Если язык программирования не поддерживает конструкцию, такую как using инструкция в C# или Visual Basic, или если вы предпочитаете не использовать ее, то можно вызвать реализацию IDisposable.Dispose из finally блока инструкции try/finally.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. В следующем примере блок using в предыдущем примере заменяется tryным блоком /finally.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

Дополнительные сведения о шаблоне finally /tryсм. в разделе try... Перехватить... Оператор finally, try-finallyили try-finally.For more information about the try/finally pattern, see Try...Catch...Finally Statement, try-finally, or try-finally Statement.

Использование IDisposableImplementing IDisposable

IDisposable следует реализовывать, только если тип использует неуправляемые ресурсы напрямую.You should implement IDisposable only if your type uses unmanaged resources directly. Потребители вашего типа могут вызывать вашу реализацию IDisposable.Dispose для освобождения ресурсов, когда экземпляр больше не нужен.The consumers of your type can call your IDisposable.Dispose implementation to free resources when the instance is no longer needed. Чтобы обрабатывать случаи, в которых они не вызывают Dispose, следует либо использовать класс, производный от SafeHandle, чтобы заключить неуправляемые ресурсы, либо переопределить метод Object.Finalize для ссылочного типа.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. В любом случае используется метод Dispose для выполнения любой очистки, необходимой после использования неуправляемых ресурсов, таких как освобождение, освобождение или сброс неуправляемых ресурсов.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 и иерархия наследованияIDisposable and the inheritance hierarchy

Базовый класс с подклассами, которые должны быть неудаляемыми, должен реализовывать IDisposable следующим образом.A base class with subclasses that should be disposable must implement IDisposable as follows. Этот шаблон следует использовать всякий раз, когда вы реализуете IDisposable для любого типа, который не sealed (NotInheritable в Visual Basic).You should use this pattern whenever you implement IDisposable on any type that isn't sealed (NotInheritable in Visual Basic).

• Он должен предоставлять один открытый, невиртуальный Dispose() метод и защищенный виртуальный Dispose(Boolean disposing) метод.It should provide one public, non-virtual Dispose() method and a protected virtual Dispose(Boolean disposing) method.

• Метод Dispose() должен вызывать Dispose(true) и отключать завершение для повышения производительности.The Dispose() method must call Dispose(true) and should suppress finalization for performance.

• базовый тип не должен включать никакие методы завершения.The base type should not include any finalizers.

Следующий фрагмент кода отражает шаблон удаления для базовых классов.The following code fragment reflects the dispose pattern for base classes. Предполагается, что тип не переопределяет метод Object.Finalize.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

Если вы переопределяете метод Object.Finalize, класс должен реализовать следующий шаблон.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

Подклассы должны реализовывать удаляемость следующим образом:Subclasses should implement the disposable pattern as follows:

• Они должны переопределить Dispose(Boolean) и вызвать реализацию базового класса Dispose(Boolean).They must override Dispose(Boolean) and call the base class Dispose(Boolean) implementation.

• при необходимости они могут предоставлять метод завершения.They can provide a finalizer if needed. Метод завершения должен вызвать Dispose(false).The finalizer must call Dispose(false).

Обратите внимание, что производные классы сами по себе не реализуют интерфейс IDisposable и не включают метод Dispose без параметров.Note that derived classes do not themselves implement the IDisposable interface and do not include a parameterless Dispose method. Они переопределяют только базовый класс Dispose(Boolean) метод.They only override the base class Dispose(Boolean) method.

Следующий фрагмент кода отражает шаблон удаления для производных классов.The following code fragment reflects the dispose pattern for derived classes. Предполагается, что тип не переопределяет метод Object.Finalize.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

Методы

Применяется к

Дополнительно

• SafeFileHandle
• Реализация метода DisposeImplementing a Dispose Method