[导入]IDisposable.Dispose 方法 [C#]
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。
void Dispose();
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。
实现此方法时，对象必须通过在包容层次结构中传播调用来进行查找，以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 反过来对 C 调用 Dispose。如果对象的基类实现了 IDisposable，对象还必须调用它们基类的 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 方法被调用多次，对象不得引发异常。如果由于资源已被释放且以前未调用 Dispose 而发生错误时，Dispose 会引发异常。
资源类型可能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。具有此类约定的类可能选择实现带有自定义名称（如 Close）的公共方法，由该方法调用 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完成器，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对象的内存之前自动调用对象的完成器。然而，在调用 Dispose 方法后，通常不需要垃圾回收器调用已处置对象的完成器。为防止自动终止，Dispose 实现可以调用 GC.SuppressFinalize 方法。
有关实现完成器的更多信息，请参见 GC 类和 Object.Finalize 方法。
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.
}
}文章来源:http://blog.163.com/fengmk2/blog/static/8913240200693115720957
