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GC.WaitForPendingFinalizers Method

Suspends the current thread until the thread processing the queue of finalizers has emptied that queue.

[Visual Basic]
Public Shared Sub WaitForPendingFinalizers()
[C#]
public static void WaitForPendingFinalizers();
[C++]
public: static void WaitForPendingFinalizers();
[JScript]
public static function WaitForPendingFinalizers();

Remarks

When the garbage collector finds objects that can be reclaimed, it checks each object to determine the object's finalization requirements. If an object implements a finalizer and has not disabled finalization by calling SuppressFinalize, the object is placed in a list of objects marked as ready for finalization. The garbage collector calls the Finalize methods for the objects in this list and removes the entries from the list. This method blocks until all finalizers have run to completion.

The thread on which finalizers are run is unspecified, so there is no guarantee that this method will terminate. However, this thread can be interrupted by another thread while the WaitForPendingFinalizers method is in progress. For example, you can start another thread that waits for a period of time then interrupts this thread if this thread is still suspended.

Example

[Visual Basic] 
Imports System

Namespace WaitForPendingFinalizersExample
   Class MyWaitForPendingFinalizersClass
  
    ' You can increase this number to fill up more memory.
      Private Const numMfos As Integer = 1000
      ' You can increase this number to cause more
      ' post-finalization work to be done.
      Private Const maxIterations As Integer = 100
     
      Overloads Shared Sub Main()
         Dim mfo As MyFinalizeObject = Nothing
      
         ' Create and release a large number of objects
         ' that require finalization.
         Dim j As Integer
         For j = 0 To numMfos - 1
            mfo = New MyFinalizeObject()
         Next j
      
         'Release the last object created in the loop.
         mfo = Nothing
      
         'Force garbage collection.
         GC.Collect()
      
         ' Wait for all finalizers to complete before continuing.
         ' Without this call to GC.WaitForPendingFinalizers, 
         ' the worker loop below might execute at the same time 
         ' as the finalizers.
         ' With this call, the worker loop executes only after
         ' all finalizers have been called.
         GC.WaitForPendingFinalizers()
      
         ' Worker loop to perform post-finalization code.
         Dim i As Integer
         For i = 0 To maxIterations - 1
            Console.WriteLine("Doing some post-finalize work")
         Next i
      End Sub
   End Class


   Class MyFinalizeObject
      ' Make this number very large to cause the finalizer to
      ' do more work.
      Private maxIterations As Integer = 10000
      
      Protected Overrides Sub Finalize()
         Console.WriteLine("Finalizing a MyFinalizeObject")
      
         ' Do some work.
         Dim i As Integer
         For i = 0 To maxIterations - 1
            ' This method performs no operation on i, but prevents 
            ' the JIT compiler from optimizing away the code inside 
            ' the loop.
            GC.KeepAlive(i)
         Next i
         MyBase.Finalize()
      End Sub
   End Class
End Namespace

[C#] 
using System;

namespace WaitForPendingFinalizersExample
{
   class MyWaitForPendingFinalizersClass
   {
    // You can increase this number to fill up more memory.
    const int numMfos = 1000;
    // You can increase this number to cause more
    // post-finalization work to be done.
    const int maxIterations = 100;

    static void Main(string[] args)
    {
       MyFinalizeObject mfo = null;
         
       // Create and release a large number of objects
       // that require finalization.
       for(int j = 0; j < numMfos; j++)
       {
          mfo = new MyFinalizeObject();
       }
         
       //Release the last object created in the loop.
       mfo = null;

       //Force garbage collection.
       GC.Collect();
         
       // Wait for all finalizers to complete before continuing.
       // Without this call to GC.WaitForPendingFinalizers, 
       // the worker loop below might execute at the same time 
       // as the finalizers.
       // With this call, the worker loop executes only after
       // all finalizers have been called.
       GC.WaitForPendingFinalizers();

       // Worker loop to perform post-finalization code.
       for(int i = 0; i < maxIterations; i++)
       {
          Console.WriteLine("Doing some post-finalize work");
       }
    }
   }

   class MyFinalizeObject
   {
    // Make this number very large to cause the finalizer to
    // do more work.
    private const int maxIterations = 10000;
      
    ~MyFinalizeObject()
    {
       Console.WriteLine("Finalizing a MyFinalizeObject");
            
       // Do some work.
       for(int i = 0; i < maxIterations; i++)
       {
          // This method performs no operation on i, but prevents 
          // the JIT compiler from optimizing away the code inside 
          // the loop.
          GC.KeepAlive(i);
       }
        }
    }
}

[C++] 
#using <mscorlib.dll>

using namespace System;

__gc class MyFinalizeObject {
   // Make this number very large to cause the finalizer to
   // do more work.
private:
   static const int  maxIterations = 10000;

   ~MyFinalizeObject() {
      Console::WriteLine(S"Finalizing a MyFinalizeObject");
      // Do some work.
      for (int i = 0; i < maxIterations; i++) {
         // This method performs no operation on i, but prevents
         // the JIT compiler from optimizing away the code inside
         // the loop.
         GC::KeepAlive( __box(i));
      }
   }
};

// You can increase this number to fill up more memory.
const int numMfos = 1000;

// You can increase this number to cause more
// post-finalization work to be done.
const int maxIterations = 100;

int main() {
   MyFinalizeObject* mfo = 0;

   // Create and release a large number of objects
   // that require finalization.
   for (int j = 0; j < numMfos; j++) {
      mfo = new MyFinalizeObject();
   }

   //Release the last object created in the loop.
   mfo = 0;

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

   // Wait for all finalizers to complete before continuing.
   // Without this call to GC::WaitForPendingFinalizers,
   // the worker loop below might execute at the same time
   // as the finalizers.
   // With this call, the worker loop executes only after
   // all finalizers have been called.
   GC::WaitForPendingFinalizers();

   // Worker loop to perform post-finalization code.
   for (int i = 0; i < maxIterations; i++) {
      Console::WriteLine(S"Doing some post-finalize work");
   }
}

[JScript] No example is available for JScript. To view a Visual Basic, C#, or C++ example, click the Language Filter button Language Filter in the upper-left corner of the page.

Requirements

Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family, .NET Compact Framework, Common Language Infrastructure (CLI) Standard

See Also

GC Class | GC Members | System Namespace

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