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Track object finalization

, 5 Jan 2011 CPOL
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Make sure your objects are garbage collected
Sometimes, it's useful to detect when an object is garbage collected.
Garbage collection happens in a separate thread, and if you want to display some information about this, in a Windows Forms GUI, you need to use BeginInvoke and not Invoke or your application will "freeze".

Invoke will not be executed during garbage collection.

#if DEBUG
  private static long objectsDestroyedCounter = 0;
  ~Entity( )
  {
    objectsDestroyedCounter++;
    if( (objectsDestroyedCounter % 10000) == 0)
    {
      LogDebug(string.Format("{0} objects dropped.",objectsDestroyedCounter) );
    }
  }
 
  private static void LogDebug(string s)
  {
    MainForm.LogString(s);
  }
 
#endif

Exceution of the code actually displaying the information is deferred until after the garbage collector has finished.

class MainForm : Form
{
  private static MainForm instance;
  
  public MainForm()
  {
  ....
    instance = this;
  }
 
  public static MainForm Instance
  {
    get
    {
      return instance; 
    }
  }
 
  public static void LogString(string s)
  {
    MainForm mainForm = Instance;
    if( mainForm != null )
    {
      Instance_MessageLogged(mainForm,s);
    }
  }
 
delegate void Instance_MessageLoggedDelegate(object sender, string message);
 
  void Instance_MessageLogged(object sender, string message)
    {
      if (InvokeRequired)
      {
        BeginInvoke(new Instance_MessageLoggedDelegate (Instance_MessageLogged), new object[] { sender, message });
      }
      else
      {
        // Excuted on the GUI thread after GC has completed
        messagesTextBox.AppendText(message);
      }
    }
}

In the hope that it might be useful,
Espen Harlinn

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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About the Author

Espen Harlinn
Architect Powel AS
Norway Norway
Chief Architect - Powel AS.

Specializing in integrated operations and high performance computing solutions.

I’ve been fooling around with computers since the early eighties, I’ve even done work on CP/M and MP/M.

Wrote my first “real” program on a BBC micro model B based on a series in a magazine at that time. It was fun and I got hooked on this thing called programming ...

A few Highlights:
  • High performance application server development
  • Model Driven Architecture and Code generators
  • Real-Time Distributed Solutions
  • C, C++, C#, Java, TSQL, PL/SQL, Delphi, ActionScript, Perl, Rexx
  • Microsoft SQL Server, Oracle RDBMS, IBM DB2, PostGreSQL
  • AMQP, Apache qpid, RabbitMQ, Microsoft Message Queuing, IBM WebSphereMQ, Oracle TuxidoMQ
  • Oracle WebLogic, IBM WebSphere
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  • AspenTech InfoPlus.21(IP21), OsiSoft PI

More information about what I do for a living can be found at: harlinn.com or LinkedIn

You can contact me at espen.harlinn@powel.no

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Comments and Discussions

 
GeneralReason for my vote of 5 Nice tip Pin
CIDev4-Jan-11 6:18
memberCIDev4-Jan-11 6:18 
GeneralReason for my vote of 5 Thanks for sharing this tip. Pin
linuxjr1-Jan-11 14:19
memberlinuxjr1-Jan-11 14:19 
GeneralThanks Pin
Espen Harlinn1-Jan-11 0:41
mvpEspen Harlinn1-Jan-11 0:41 
GeneralReason for my vote of 5 Good Pin
Shahin Khorshidnia31-Dec-10 16:30
memberShahin Khorshidnia31-Dec-10 16:30 
GeneralCarefull when you do this... Pin
msmits10-Jan-11 1:52
membermsmits10-Jan-11 1:52 
GeneralRe: Carefull when you do this... Pin
Espen Harlinn10-Jan-11 2:27
memberEspen Harlinn10-Jan-11 2:27 
GeneralRe: Carefull when you do this... Pin
msmits10-Jan-11 3:01
membermsmits10-Jan-11 3:01 
Hi Espen,

Putting debug stuff inside compiler directives is a good thing indeed.

My point about the GC is that by adding a finalizer you are changing the GC behavior.

First, when GC detects your object is not used, it is put on a list for finalization, as well as 'upgrading' the generation (0-2) of the object.
A seperate thread will (at some undeterminable point) call the finalizer and mark the object as 'finalized'.
Later, when GC decides to do a higher generation cleanup (in other words, under memory pressure), it will find this object and free its memory.
This may be at a much later time.

So in short, just because the finalizer is called does not mean the object is cleaned up.
Sorry for this really short/blunt explanation, there's more to .NET memory management than this Wink | ;-)

If you're using .NET caches, they have a way of being notified when the cache is cleared.
The idea of these notifications is to check whether you want to extend their lifetime, but I guess logging should fit nicely in there as well.
Don't know if this might help you but I thought I mention it.

Cheers,
Michel
GeneralRe: Carefull when you do this... Pin
Espen Harlinn10-Jan-11 3:35
memberEspen Harlinn10-Jan-11 3:35 
GeneralRe: Carefull when you do this... Pin
msmits10-Jan-11 3:43
membermsmits10-Jan-11 3:43 
GeneralRe: Carefull when you do this... Pin
Espen Harlinn10-Jan-11 3:52
memberEspen Harlinn10-Jan-11 3:52 

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