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

定義

執行與釋放 (Free)、釋放 (Release) 或重設 Unmanaged 資源相關聯之應用程式定義的工作。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 ()

範例

下列範例示範如何實作Dispose方法。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

備註

使用此方法來關閉或釋放 unmanaged 的資源,例如檔案、 資料流,以及實作此介面之類別的執行個體所持有的控制代碼。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. 依照慣例,這個方法用於所有與釋放物件所持有的資源相關聯的工作或準備重複使用的物件。By convention, this method is used for all tasks associated with freeing resources held by an object, or preparing an object for reuse.

警告

如果您使用的類別可實作IDisposable介面,您應該呼叫其Dispose當您完成使用類別的實作。If you are using a class that implements the IDisposable interface, you should call its Dispose implementation when you are finished using the class. 如需詳細資訊,請參閱中的 < 使用實作 IDisposable 的物件 > 一節IDisposable主題。For more information, see the "Using an object that implements IDisposable" section in the IDisposable topic.

當實作這個方法,請確定所有保留的資料傳播透過內含項目階層架構的呼叫所釋出資源。When implementing this method, ensure that all held resources are freed by propagating the call through the containment hierarchy. 例如,如果物件的配置物件 B,而物件 B 會配置物件 C,然後 ADispose實作必須呼叫Disposeb,它必須接著呼叫Dispose上 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.

重要

C + + 編譯器支援決定性的資源處置,而且不允許直接實作Dispose方法。The C++ compiler supports deterministic disposal of resources and does not allow direct implementation of the Dispose method.

物件還必須呼叫Dispose如果基底類別實作其基底類別方法IDisposableAn object must also call the Dispose method of its base class if the base class implements IDisposable. 如需實作的詳細資訊IDisposable上的基底類別和子類別,請參閱中的 < IDisposable 和繼承階層架構 > 一節IDisposable主題。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.

如果物件的Dispose超過一次呼叫方法,該物件必須忽略所有呼叫第一個。If an object's Dispose method is called more than once, the object must ignore all calls after the first one. 物件不能擲回例外狀況如果其Dispose多次呼叫方法。The object must not throw an exception if its Dispose method is called multiple times. 執行個體方法以外Dispose可能會擲回ObjectDisposedException時已經處置資源。Instance methods other than Dispose can throw an ObjectDisposedException when resources are already disposed.

使用者可能預期資源類型,用以代表已配置的狀態,釋放的狀態與特定的慣例。Users might expect a resource type to use a particular convention to denote an allocated state versus a freed state. 這個範例是資料流類別,以傳統上視為開啟或關閉。An example of this is stream classes, which are traditionally thought of as open or closed. 具有這類的慣例的類別的實作器可能會選擇實作的公用方法,以自訂名稱,例如Close,以呼叫Dispose方法。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.

因為Dispose必須明確地呼叫方法,一律會有危險的 unmanaged 的資源並不會釋放,因為物件的取用者無法呼叫其Dispose方法。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. 有兩種方式可避免這個問題:There are two ways to avoid this:

當您使用的物件,例如存取 unmanaged 的資源, StreamWriter,理想的作法是建立與執行個體using陳述式。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. using陳述式就會自動關閉資料流並呼叫Dispose物件正在使用它的程式碼完成時。The using statement automatically closes the stream and calls Dispose on the object when the code that is using it has completed. 如需範例,請參閱StreamWriter類別。For an example, see the StreamWriter class.

適用於

另請參閱