Small question on Finalizers - C# Discussion Boards

Re: The class MediaPlayer of namespace System.Windows.Media can't play music on OS Windows XP

2-Jun-16 20:03

Check your application build settings, and change them from "any cpu" to "x86".
That will force it to build as a 32 bit app, and the WMP control should work.

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Member 111473382-Jun-16 20:16

Member 11147338

2-Jun-16 20:16

Thanks for your reply ,in fact,I changed the build settings from "any cpu" to "x86",otherwise ,the app can't run.

Small question on Finalizers

Foothill2-Jun-16 8:56

2-Jun-16 8:56

Can I use finalizers as a backup for when IDisposable objects are not properly disposed?

I'll use a class that contains a thread as an example

public sealed class TaskExecuter : IDisposable
{
  private Thread _thread;
  //... other class members such as Actions and WaitHandles
  //... all the other things that this class does

  // last ditch effort to ensure resources are cleaned up
  ~TaskExecuter()
  {
    if (_thread != null && _thread.ThreadState != ThreadState.Stopped)
    {
      //... if not null, dispose of managed system objects.
      _thread.Join();
    }
  }

  private void Dispose(bool disposing)
  {
    if (disposing)
    {
      //... release other system objects such as wait handles
      _thread.Join(1000);
    }
  }

  public void Dispose()
  {
    Dispose(true);
    GC.SupressFinalize(this);
  }
}

So in this case, the class has a thread that it can reuse through the lifespan of the class. What I am concerned with is what if I or another developer creates this class, uses it, and forgets to dispose of it. This would leave the thread in an uncontrollable state and not to mention certain other system objects until the program is terminated.

Can I prevent this by making other checks in a finalizer?

if (Object.DividedByZero == true) { Universe.Implode(); }
Meus ratio ex fortis machina. Simplicitatis de formae ac munus. -Foothill, 2016

Dave Kreskowiak2-Jun-16 9:07

Dave Kreskowiak

2-Jun-16 9:07

It can so long as your Finalize code doesn't mind being executed on a separate thread other than the one that created your instance and you don't care when the Finalizer gets called because you don't have control over it and it may take a good chunk of time after the object is flagged as dead before it gets called.

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Dave Kreskowiak

Foothill2-Jun-16 9:55

2-Jun-16 9:55

Ah, so would Thread.Join() throw an access exception if called in the finalizer? In the case that I working on, it doesn't matter when the finalizer gets called. I am just looking for ways to ensure that threads and other system objects get disposed of in the event that Dispose() does not get called before the object goes out of scope.

if (Object.DividedByZero == true) { Universe.Implode(); }
Meus ratio ex fortis machina. Simplicitatis de formae ac munus. -Foothill, 2016

Dave Kreskowiak2-Jun-16 10:53

Dave Kreskowiak

2-Jun-16 10:53

Access exception? Probably not, but calling Join in the Finalizer is definitely a bad idea.

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Dave Kreskowiak

Foothill2-Jun-16 11:22

2-Jun-16 11:22

Well, in that regard, I have another question. To explain a little more on the use-case that orginated this question, I have built a ThreadPool that spawns and terminates threads as it sees fit and it works well for that purpose. Up until now, I have been the only one to use that code but it might be making it's way into a larger library and I want to protect against the eventuality of a forgetful programmer. Is there a safe way to shut down those threads from the finalizer or is it better to safely abstract that away from the API?

if (Object.DividedByZero == true) { Universe.Implode(); }
Meus ratio ex fortis machina. Simplicitatis de formae ac munus. -Foothill, 2016

Dave Kreskowiak2-Jun-16 11:58

Dave Kreskowiak

2-Jun-16 11:58

OK, you're trying to protect the programmer from her/his self. It gets to the point where you're going overboard to protect someone who should know better. We all know (if we know what we're doing that is) if the object exposes a Dispose, you call it. Simple as that. Trying to make sure an idiot can use your code without issues just puts all of the work on you and none of the work on them, for what gain?

Can it be done from the Finalizer, sure. Is it a good idea? No. Can the user still run the system out of resources? Yep, because you cannot deterministically force a Finalize. The GC will get around to it whenever it feels like it and that may be AFTER the system has run out of a resource.

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Foothill3-Jun-16 5:10

3-Jun-16 5:10

I see your point. Do what you can to ensure things run right but don't waste a lot of time on the what if scenarios.

if (Object.DividedByZero == true) { Universe.Implode(); }
Meus ratio ex fortis machina. Simplicitatis de formae ac munus. -Foothill, 2016

Richard Deeming2-Jun-16 9:34

Richard Deeming

2-Jun-16 9:34

You should definitely read Eric Lippert's two blog posts on finalizers:
When everything you know is wrong, part one | Fabulous adventures in coding[^]
When everything you know is wrong, part two | Fabulous adventures in coding[^]

Particularly this part:

Quote:
If you have a tree of objects and you are finalizing the root, then the children are still alive — because the root is alive, because it is on the finalization queue, and so the children have a living reference — but the children may have already been finalized, and are in no particularly good state to have their methods or data accessed.

Also:

Garbage Collector Basics and Performance Hints[^]:

Therefore, it is vitally important that finalizers do as little work as possible. Remember also that although all object pointers remain valid during finalization, it might be the case that those pointers lead to objects that have already been finalized and might therefore be less than useful. It is generally safest to avoid following object pointers in finalization code even though the pointers are valid. A safe, short finalization code path is the best.

And:

Chapter 5 - Improving Managed Code Performance[^]:

* Implement Finalize only if you hold unmanaged resources across client calls.
* Keep finalizer code simple to prevent blocking.
- Do not issue calls that could block the calling thread.

Basically, calling Thread.Join from a finalizer seems like a very bad idea. Smile | :)

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Foothill2-Jun-16 11:02

How to convert pounds(Lb) to ounce(Oz) and Ounce(Oz) to Pounds(Lb) in C#.Net code

2-Jun-16 11:02

Chapter 5 really helped to clear up some of my confusion with finalizers. I don't know why but it was easier to understand then the articles on IDisposable or garbage collection as neither of them really adequately explained the 'why' of the dispose pattern. I realized that if an unmanged resource is persisted for a lengthy period of time during execution, implement the Dispose pattern and put a Dispose call in the finalizer to ensure that any Win32 Handles (theads and such) get released back to the OS.

I also finally understand the reason for all those GG.SuppressFinalize(this) calls I've seen spattered about the internet. You put a backup Dispose() call in the finalizer but if you remember to call your normal Dispose(), the finalizer shouldn't be called because it would throw the ObjectAlreadyDisposed exception.

I swear, sometimes you can stare at the same articles on Garbage Collection and IDisposable dozens of times without parsing the whole concept together then one time, bang, "Oh, that's why it works that way!?" D'Oh! | :doh:

Thanks for the links. They were very informative.

if (Object.DividedByZero == true) { Universe.Implode(); }
Meus ratio ex fortis machina. Simplicitatis de formae ac munus. -Foothill, 2016

somagunasekaran2-Jun-16 1:35

somagunasekaran

2-Jun-16 1:35

Hi Team,

I am working on unit of measure..
Just I want to know that logic part of the C#.Net source code for convert to Lb to Oz and Oz to Lb in drop down.

If you are selecting as LB in one of the drop down and one more drop down selecting as a Oz and total converting calculation will be displayed in one of the text box.

Please let me know how to convert this logic part.
I am struggling now this logic part in drop down.

Thanks
Somasundaram

I want to join in the website

Re: How to convert pounds(Lb) to ounce(Oz) and Ounce(Oz) to Pounds(Lb) in C#.Net code

Richard Deeming2-Jun-16 2:11

Richard Deeming

2-Jun-16 2:11

1lb = 16oz

If you're converting from lb to oz, multiply by 16.
If you're converting from oz to lb, divide by 16.

(Assuming you're not using Troy pounds/ounces[^].)

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- Homer

Re: How to convert pounds(Lb) to ounce(Oz) and Ounce(Oz) to Pounds(Lb) in C#.Net code

OriginalGriff2-Jun-16 4:08

Re: How to convert pounds(Lb) to ounce(Oz) and Ounce(Oz) to Pounds(Lb) in C#.Net code

2-Jun-16 4:08

There's no real "logic part" in the operation: it's all about identifying what the conversion factor is.
I'm just guessing that you're a beginner and this is homework - so I won't explain how I'd do it (it probably involves some bits you haven't got to yet) and suggest that you pick a "base unit" and provide each possible "convertable unit" with a value which converts to that base unit. For example, if you select the kilogram as your base unit, then the conversion factor for 1lb would be 2.20462, and the conversion factor for 1oz would be 35.274
So to convert from "unit a" to "unit b" you multiply the number of items by the "unit b" conversion factor, divide that by the "unit a" convertion factor, and round it to perhaps 2 decimal places.
If the number of lb is 6.0, then you would convert to oz by:

6.0 * 35.274 / 2.20462 = 96.0002177246

Rounded, that's 96.00 oz.
So all you need to do is write a method which takes the selected unit text, and returns the conversion factor. Then call that twice, and you're pretty much there!

Try it: it's simpler than it sounds!

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Richard MacCutchan2-Jun-16 4:35

Richard MacCutchan

2-Jun-16 4:35

OriginalGriff wrote:
I'm just guessing that you're a beginner

See description at somagunasekaran - Professional Profile - CodeProject[^].

Re: How to convert pounds(Lb) to ounce(Oz) and Ounce(Oz) to Pounds(Lb) in C#.Net code

OriginalGriff2-Jun-16 4:57

Re: How to convert pounds(Lb) to ounce(Oz) and Ounce(Oz) to Pounds(Lb) in C#.Net code

2-Jun-16 4:57

THREE YEARS!

And he can't do that on his own?
Elephant! WTF | :WTF:

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Pete O'Hanlon2-Jun-16 5:37

Pete O'Hanlon

2-Jun-16 5:37

Be fair, he said it was three years in the field. Very possibly there was no computer in this field. Perhaps there were some sheep.

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Re: How to convert pounds(Lb) to ounce(Oz) and Ounce(Oz) to Pounds(Lb) in C#.Net code

OriginalGriff2-Jun-16 6:05