IDisposable.Dispose 方法
执行与释放或重置非托管资源相关的应用程序定义的任务。
**命名空间:**System
**程序集:**mscorlib（在 mscorlib.dll 中）
语法
声明
Sub Dispose
用法
Dim instance As IDisposable
instance.Dispose
void Dispose ()
void Dispose ()
void Dispose ()
function Dispose ()
备注
使用此方法关闭或释放由实现此接口的类的实例保持的文件、流和句柄等非托管资源。根据约定，此方法用于与释放对象保持的资源或准备对象以便重新使用有关的所有任务。
.gif) 重要事项： |
|---|
C++ 程序员应当阅读 Destructors and Finalizers in Visual C++。在 .NET Framework 2.0 版中，C++ 编译器为实现资源的确定释放提供支持，同时不允许 Dispose 方法的直接实现。 |
实现此方法时，可通过在包容层次结构中传播调用来确保释放所有保持的资源。例如，如果对象 A 分配对象 B，而对象 B 又分配对象 C，那么 A 的 Dispose 实现必须对 B 调用 Dispose，而 B 反过来必须对 C 调用 Dispose。如果一个对象的基类实现 IDisposable，该对象还必须调用其基类的 Dispose 方法。
如果某对象的 Dispose 方法被调用一次以上，则该对象必须忽略第一次调用后的所有调用。如果对象的 Dispose 方法被多次调用，该对象一定不要引发异常。除 Dispose 之外的实例方法在资源已释放时会引发 ObjectDisposedException。
用户可能期望资源类型使用特定的约定来表示已分配状态和已释放状态。流类即是这样一种示例，传统上认为它们要么打开要么关闭。具有此种约定的类的实施者可能选择实现具有自定义名称（如“Close”）的公用方法来调用 Dispose 方法。
因为 Dispose 方法必须显式进行调用，所以，实现 IDisposable 的对象还必须实现一个终结器，以便在未调用 Dispose 时处理释放资源问题。默认情况下，垃圾回收器会在回收一个对象的内存之前自动调用该对象的终结器。然而，在调用 Dispose 方法后，通常不需要垃圾回收器调用已释放对象的终结器。为防止自动终止，Dispose 实现可以调用 GC.SuppressFinalize 方法。
有关实现终结器和 Dispose 方法的更多信息，请参见 GC 类、Object.Finalize 方法和 实现 Finalize 和 Dispose 以清理非托管资源。
示例
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.
Private 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
End If
disposed = True
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
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.
private 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;
}
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.
}
}
#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();
}
import System.*;
import 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 static class MyResource implements 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 boolean disposed = false;
// The class constructor.
public MyResource(IntPtr handle)
{
this.handle = handle;
} //MyResource
// 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
// 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.
private void Dispose(boolean 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;
}
disposed = true;
} //Dispose
// Use interop to call the method necessary
// to clean up the unmanaged resource.
/** @attribute System.Runtime.InteropServices.DllImport("Kernel32")
*/
private static native Boolean CloseHandle(IntPtr handle);
// Use J# 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.
public void finalize()
{
// Do not re-create Dispose clean-up code here.
// Calling Dispose(false) is optimal in terms of
// readability and maintainability.
Dispose(false);
try {
super.finalize();
}
catch(System.Exception e ) {
}
} //finalize
} //MyResource
public static void main(String[] args)
{
// Insert code here to create
// and use the MyResource object.
} //main
} //DisposeExample
平台
Windows 98、Windows 2000 SP4、Windows CE、Windows Millennium Edition、Windows Mobile for Pocket PC、Windows Mobile for Smartphone、Windows Server 2003、Windows XP Media Center Edition、Windows XP Professional x64 Edition、Windows XP SP2、Windows XP Starter Edition
.NET Framework 并不是对每个平台的所有版本都提供支持。有关受支持版本的列表，请参见系统要求。
版本信息
.NET Framework
受以下版本支持：2.0、1.1、1.0
.NET Compact Framework
受以下版本支持：2.0、1.0