IDisposable.Dispose 方法

定义

执行与释放或重置非托管资源关联的应用程序定义的任务。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 ()

示例

下面的示例演示如何实现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.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

注解

使用此方法可关闭或释放由实现该接口的类的实例所持有的非托管资源, 如文件、流和句柄。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. 按照约定, 此方法用于与释放对象占用的资源或准备要重用的对象相关联的所有任务。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

如果使用的是实现IDisposable接口的类, 则应在使用完类后调用其Dispose实现。If you are using a class that implements the IDisposable interface, you should call its Dispose implementation when you are finished using the class. 有关详细信息, 请参阅IDisposable主题中的 "使用实现 IDisposable 的对象" 一节。For more information, see the "Using an object that implements IDisposable" section in the IDisposable topic.

实现此方法时, 请确保通过包含层次结构传播调用来释放所有保存的资源。When implementing this method, ensure that all held resources are freed by propagating the call through the containment hierarchy. 例如, 如果对象 A 分配一个对象 b, 并且对象 b 分配一个对象 C, 则的Dispose实现必须在 B 上调用Dispose , Dispose后者必须在 C 上调用。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++编译器支持对资源进行确定性处置, 并且不允许直接实现Dispose方法。The C++ compiler supports deterministic disposal of resources and does not allow direct implementation of the Dispose method.

如果基类实现Dispose IDisposable, 则对象还必须调用其基类的方法。An object must also call the Dispose method of its base class if the base class implements IDisposable. 有关在基类及其子类IDisposable上实现的详细信息, 请参阅IDisposable主题中的 "IDisposable and 继承性层次结构" 部分。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.

如果多次调用对象Dispose的方法, 则对象必须忽略第一个调用之后的所有调用。If an object's Dispose method is called more than once, the object must ignore all calls after the first one. 如果对象的Dispose方法被多次调用, 则该对象不得引发异常。The object must not throw an exception if its Dispose method is called multiple times. Dispose外的ObjectDisposedException实例方法可以在已释放资源时引发。Instance methods other than Dispose can throw an ObjectDisposedException when resources are already disposed.

用户可能希望资源类型使用特定约定来表示已分配状态与已释放状态。Users might expect a resource type to use a particular convention to denote an allocated state versus a freed state. 这种情况的一个示例是流类, 通常将其视为 "打开" 或 "已关闭"。An example of this is stream classes, which are traditionally thought of as open or closed. 具有此类约定的类的实施者可能选择使用自定义名称 (例如Close) 来实现公共方法, 以Dispose调用方法。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.

由于方法必须被显式调用, 因此, 始终不会释放非托管资源, 因为对象的使用者无法调用其Dispose方法。 DisposeBecause 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. 可以通过两种方法来避免这种情况:There are two ways to avoid this:

使用访问非托管资源的对象 (例如StreamWriter) 时, 一个好的做法是using使用语句创建实例。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. 语句会自动关闭流, 并在使用对象的代码已完成时调用DisposeusingThe using statement automatically closes the stream and calls Dispose on the object when the code that is using it has completed. 有关示例, 请参阅StreamWriter类。For an example, see the StreamWriter class.

适用于

另请参阅