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GC.WaitForPendingFinalizers Method

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

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

public static void WaitForPendingFinalizers()

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 that are 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 and then interrupts this thread if this thread is still suspended.

The following example demonstrates how to use the WaitForPendingFinalizers method to suspend the current thread until finalization of all the collected objects is complete.

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);
	   }
        }
    }
}

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

.NET for Windows Store apps

Supported in: Windows 8

Supported in: Windows Phone 8.1

Supported in: Windows Phone Silverlight 8.1

Supported in: Windows Phone Silverlight 8

Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

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

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