GC.ReRegisterForFinalize Method (System)

ReRegisterForFinalize Method

Collapse All

Language Filter

This page is specific to

Microsoft Visual Studio 2008/.NET Framework 3.5

Other versions are also available for the following:

.NET Framework Class Library

GC..::.ReRegisterForFinalize Method

Updated: November 2007

Requests that the system call the finalizer for the specified object for which SuppressFinalize has previously been called.

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

Syntax

Visual Basic (Declaration)

Public Shared Sub ReRegisterForFinalize ( _
    obj As Object _
)

Visual Basic (Usage)

Dim obj As Object

GC.ReRegisterForFinalize(obj)

public static void ReRegisterForFinalize(
    Object obj
)

Visual C++

public:
static void ReRegisterForFinalize(
    Object^ obj
)

public static void ReRegisterForFinalize(
    Object obj
)

JScript

public static function ReRegisterForFinalize(
    obj : Object
)

Parameters

obj: Type: System..::.Object
The object that a finalizer must be called for.

Exceptions

Exception	Condition
ArgumentNullException	obj is nullNothingnullptra null reference (Nothing in Visual Basic).

Remarks

The ReRegisterForFinalize method adds the obj parameter to the list of objects that request finalization before the garbage collector frees the object. The obj parameter must be the caller of this method.

Calling the ReRegisterForFinalize method does not guarantee that the garbage collector will call an object's finalizer.

By default, all objects that implement finalizers are added to the list of objects that require finalization; however, an object might have already been finalized or might have disabled finalization by calling the SuppressFinalize method.

A finalizer can use this method to resurrect itself or an object that it references.

Examples

The following example demonstrates how to use the ReRegisterForFinalize method to finalize an object a second time after garbage collection.

Visual Basic

Imports System

Namespace ReRegisterForFinalizeExample
    Class MyMainClass
        Shared Sub Main()
            'Create a MyFinalizeObject.
            Dim mfo As New MyFinalizeObject()

            'Release the reference to mfo.
            mfo = Nothing

            'Force a garbage collection.
            GC.Collect()

            'At this point mfo will have gone through the first Finalize.
            'There should now be a reference to mfo in the static
            'MyFinalizeObject.currentInstance field.  Setting this value
            'to null and forcing another garbage collection will now
            'cause the object to Finalize permanently.
            MyFinalizeObject.currentInstance = Nothing
            GC.Collect()
        End Sub
    End Class

    Class MyFinalizeObject
        Public Shared currentInstance As MyFinalizeObject = Nothing
        Private hasFinalized As Boolean = False

        Protected Overrides Sub Finalize()
            If hasFinalized = False Then
                Console.WriteLine("First finalization")

                'Put this object back into a root by creating
                'a reference to it.
                MyFinalizeObject.currentInstance = Me

                'Indicate that this instance has finalized once.
                hasFinalized = True

                'Place a reference to this object back in the
                'finalization queue.
                GC.ReRegisterForFinalize(Me)
            Else
                Console.WriteLine("Second finalization")
            End If
            MyBase.Finalize()
        End Sub
    End Class
End Namespace

using System;

namespace ReRegisterForFinalizeExample
{
    class MyMainClass
    {
        static void Main()
        {
            // Create a MyFinalizeObject.
            MyFinalizeObject mfo = new MyFinalizeObject();

            // Release the reference to mfo.
            mfo = null;

            // Force a garbage collection.
            GC.Collect();

            // At this point mfo will have gone through the first Finalize.
            // There should now be a reference to mfo in the static
            // MyFinalizeObject.currentInstance field.  Setting this value
            // to null and forcing another garbage collection will now
            // cause the object to Finalize permanently.
            MyFinalizeObject.currentInstance = null;
            GC.Collect();
        }
    }

    class MyFinalizeObject
    {
        public static MyFinalizeObject currentInstance = null;
        private bool hasFinalized = false;

        ~MyFinalizeObject()
        {
            if(hasFinalized == false)
            {
                Console.WriteLine("First finalization");

                // Put this object back into a root by creating
                // a reference to it.
                MyFinalizeObject.currentInstance = this;

                // Indicate that this instance has finalized once.
                hasFinalized = true;

                // Place a reference to this object back in the
                // finalization queue.
                GC.ReRegisterForFinalize(this);
            }
            else
            {
                Console.WriteLine("Second finalization");
            }
        }
    }
}

Visual C++

using namespace System;
ref class MyFinalizeObject
{
public:
   static MyFinalizeObject^ currentInstance = nullptr;

private:
   bool hasFinalized;

public:
   MyFinalizeObject()
   {
      hasFinalized = false;
   }

   ~MyFinalizeObject()
   {
      if ( hasFinalized == false )
      {
         Console::WriteLine( "First finalization" );

         // Put this object back into a root by creating
         // a reference to it.
         MyFinalizeObject::currentInstance = this;

         // Indicate that this instance has finalized once.
         hasFinalized = true;

         // Place a reference to this object back in the
         // finalization queue.
         GC::ReRegisterForFinalize( this );
      }
      else
      {
         Console::WriteLine( "Second finalization" );
      }
   }

};

int main()
{

   // Create a MyFinalizeObject.
   MyFinalizeObject^ mfo = gcnew MyFinalizeObject;

   // Release the reference to mfo.
   mfo = nullptr;

   // Force a garbage collection.
   GC::Collect();

   // At this point mfo will have gone through the first Finalize.
   // There should now be a reference to mfo in the static
   // MyFinalizeObject::currentInstance field.  Setting this value
   // to 0 and forcing another garbage collection will now
   // cause the object to Finalize permanently.
   MyFinalizeObject::currentInstance = nullptr;
   GC::Collect();
}

package ReRegisterForFinalizeExample;

import System.* ;

class MyMainClass
{
    public static void main(String[] args)
    {
        // Create a MyFinalizeObject.
        MyFinalizeObject mfo = new MyFinalizeObject();

        // Release the reference to mfo.
        mfo = null;

        // Force a garbage collection.
        GC.Collect();

        // At this point mfo will have gone through the first Finalize.
        // There should now be a reference to mfo in the static
        // MyFinalizeObject.currentInstance field.  Setting this value
        // to null and forcing another garbage collection will now
        // cause the object to Finalize permanently.
        MyFinalizeObject.currentInstance = null;
        GC.Collect();
    } //main
} //MyMainClass

class MyFinalizeObject
{
    public static MyFinalizeObject currentInstance = null;
    private boolean hasFinalized = false;

    public void finalize()
    {
        if (hasFinalized == false) {
            Console.WriteLine("First finalization");

            // Put this object back into a root by creating
            // a reference to it.
            MyFinalizeObject.currentInstance = this;

            // Indicate that this instance has finalized once.
            hasFinalized = true;

            // Place a reference to this object back in the
            // finalization queue.
            GC.ReRegisterForFinalize(this);
        }
        else {
            Console.WriteLine("Second finalization");
        }

        try {
            super.finalize();
        }
        catch (System.Exception e) {
            Console.WriteLine(e.get_Message());
        }
    } //finalize
} //MyFinalizeObject

Platforms

Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

Version Information