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GC.SuppressFinalize Method

Requests that the system not call the finalizer for the specified object.

Namespace: System
Assembly: mscorlib (in mscorlib.dll)

public:
static void SuppressFinalize (
	Object^ obj
)
public static void SuppressFinalize (
	Object obj
)
public static function SuppressFinalize (
	obj : Object
)
Not applicable.

Parameters

obj

The object that a finalizer must not be called for.

Exception typeCondition

ArgumentNullException

obj is a null reference (Nothing in Visual Basic).

This method sets a bit in the object header, which the system checks when calling finalizers. The obj parameter is required to be the caller of this method.

Objects that implement the IDisposable interface can call this method from the IDisposable.Dispose method to prevent the garbage collector from calling Object.Finalize on an object that does not require it.

The following example demonstrates how to use the SuppressFinalize method in a resource class to prevent a redundant garbage collection from being called.

#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 use the
// GC::SuppressFinalize method to prevent finalization of an
// object that has been disposed. For C++, the call to 
// GC::SuppressFinalize is not explicit; it is emitted by the
// compiler, in the Dispose() method. The comments in this code
// example explain where that call occurs and its part in the
// overall Dispose/Finalize pattern.
//
// The code example demonstrates how to create a class that 
// implements the IDisposable interface and the IDisposable.Dispose
// method. By implementing IDisposable, you are announcing that
// instances of this type allocate scarce resources, which can be
// released by calling Dispose() when the programmer is finished 
// with the object or which will be released when the finalizer
// is executed. 
//
// Note that for This code example 
//
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;
   }

   // In managed code, the destructor contains code to clean up managed
   // resources. This method is called by Dispose(bool disposing), 
   // which the C++ compiler emits for you when you implement the 
   // destructor; it is only called if disposing == true -- that is, 
   // if the user has called Dispose(). (In C++, the user calls 
   // ~MyResource(), which the compiler emits as a call to Dispose().)
   // The emitted Dispose() method calls GC::SuppressFinalize( this )
   // for you, so there is no need to call it here.
   ~MyResource() 
   {
      // Dispose of managed resources.
      component->~Component();

      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 );

   // Note: The Dispose(bool disposing) method emitted by the 
   // compiler executes in two distinct scenarios. If disposing ==
   // true, the method has been called directly or indirectly by a 
   // user's code. Managed and unmanaged resources can be disposed,
   // so both ~MyResource() and !MyResource() are called.
   //
   // 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, so
   // only !MyResource() is called.

   // This destructor runs when the Dispose method gets called 
   // explicitly, and also when (and if) the Finalizer is run.
   !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 use the 
// GC.SuppressFinalize method in a resource class to prevent
// the clean-up code for the object from being called twice.
public class DisposeExample
{
    // A 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 VJ# 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 a MyResource object.
    } //main
} //DisposeExample

Windows 98, Windows Server 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

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0, 1.0

XNA Framework

Supported in: 1.0

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