IDisposable Интерфейс
Определение
Предоставляет механизм для освобождения неуправляемых ресурсов.Provides a mechanism for releasing unmanaged resources.
public interface class IDisposable
public interface IDisposable
[System.Runtime.InteropServices.ComVisible(true)]
public interface IDisposable
type IDisposable = interface
[<System.Runtime.InteropServices.ComVisible(true)>]
type IDisposable = interface
Public Interface IDisposable
- Производный
- Атрибуты
Примеры
В следующем примере показано, как создать класс ресурсов, реализующий IDisposable интерфейс.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 Dispose метод этого интерфейса для явного освобождения неуправляемых ресурсов 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.
Предупреждение
Это коренное изменение для добавления IDisposable интерфейса в существующий класс.It is a breaking change to add the IDisposable interface to an existing class. Поскольку уже существующие потребители типа не могут вызывать Dispose , нельзя быть уверенным, что неуправляемые ресурсы, удерживаемые типом, будут освобождены.Because pre-existing consumers of your type cannot call Dispose, you cannot be certain that unmanaged resources held by your type will be released.
Поскольку IDisposable.Dispose реализация вызывается потребителем типа, когда ресурсы, принадлежащие экземпляру, больше не требуются, следует либо обернуть управляемый объект в SafeHandle (рекомендуемый альтернативный вариант), либо переопределять Object.Finalize для освобождения неуправляемых ресурсов в событии, которое пользователь забыл 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.
Важно!
В .NET Framework компилятор C++ поддерживает детерминированное удаление ресурсов и не допускает прямую реализацию Dispose метода.In the .NET Framework, the C++ compiler supports deterministic disposal of resources and does not allow direct implementation of the Dispose method.
Подробное обсуждение использования этого интерфейса и Object.Finalize метода 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 IDisposable интерфейс, следует вызвать реализацию объекта, IDisposable.Dispose 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
using
оператор в C# и Visual Basic.By using a language construct such as theusing
statement in C# and Visual Basic.Путем заключения вызова в IDisposable.Dispose реализацию в
try
/finally
блоке.By wrapping the call to the IDisposable.Dispose implementation in atry
/finally
block.
Примечание
Документация по типам, которые реализуют IDisposable , обратите внимание на то, что в действительности и включает напоминание для вызова его Dispose реализации.Documentation for types that implement IDisposable note that fact and include a reminder to call its Dispose implementation.
Инструкции 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, сохраняющего 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
Эта using
инструкция 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
/ finally
блока.At compile time, the language compiler implements the intermediate language (IL) for a try
/finally
block.
Дополнительные сведения об 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, подобную using
инструкции в C# или Visual Basic, или если вы предпочитаете не использовать ее, можно вызвать IDisposable.Dispose реализацию из finally
блока try
/ finally
инструкции.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. Следующий пример заменяет using
блок в предыдущем примере try
/ finally
блоком.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 try
/ finally
шаблоне см. 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
Следует реализовывать, IDisposable 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 IDisposable.Dispose реализацию 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 ошибку Dispose , следует использовать класс, производный от, SafeHandle чтобы создать оболочку для неуправляемых ресурсов, или переопределить Object.Finalize метод 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 Dispose метод 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.
Важно!
При определении базового класса, использующего неуправляемые ресурсы и имеющего или, скорее всего, подклассов, которые должны быть удалены, следует реализовать IDisposable.Dispose метод и предоставить вторую перегрузку Dispose
, как описано в следующем разделе.If you are defining a base class that uses unmanaged resources and that either has, or is likely to have, subclasses that should be disposed, you should implement the IDisposable.Dispose method and provide a second overload of Dispose
, as discussed in the next section.
IDisposable и иерархия наследованияIDisposable and the inheritance hierarchy
Базовый класс с подклассами, которые должны быть уничтожены, должен реализовываться IDisposable следующим образом.A base class with subclasses that should be disposable must implement IDisposable as follows. Этот шаблон следует использовать при реализации IDisposable любого типа, который не является 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, не виртуальный Dispose() метод и защищенный виртуальный
Dispose(Boolean disposing)
метод.It should provide one public, non-virtual Dispose() method and a protected virtualDispose(Boolean disposing)
method.Dispose()Метод должен вызывать
Dispose(true)
и отключать завершение для повышения производительности.The Dispose() method must callDispose(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 Object.Finalize метод.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
При переопределении Object.Finalize метода 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 переопределять
Dispose(Boolean)
и вызвать реализациюDispose(Boolean)
базового класса;They must overrideDispose(Boolean)
and call the base classDispose(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 callDispose(false)
.
Обратите внимание, что производные классы сами по себе не реализуют IDisposable интерфейс и не включают метод без параметров Dispose .Note that derived classes do not themselves implement the IDisposable interface and do not include a parameterless Dispose method. Они переопределяют только метод базового класса Dispose(Boolean)
.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 Object.Finalize метод.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
Dispose() |
Выполняет определяемые приложением задачи, связанные с удалением, высвобождением или сбросом неуправляемых ресурсов.Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources. |