Nicholas Paldino [.NET/C# MVP]
5/16/2007 8:08:00 PM
See inline:
> 1) How come in .NET 1.1, the COM object is not released even after I
> called gc.Collect multiple times as following
>
> GC.Collect();
> GC.WaitForPendingFinalizers();
> GC.Collect();
>
> If the above code releases the COM object, I would not be so puzzled.
>
> But in .NET 2.0 it was release right away.
Without seeing the rest of the code, it is impossible to say, but the
only reason the COM reference would be sticking around is if something was
holding a reference to the wrapper and that wrapper had not been passed to
ReleaseComObject.
> 2) In our code, we have one method, take the COM object, stored it in
> an ArrayList, in the second method , we take the same COM object, here
> we search the ArrayList, remove the COM object from the ArrayList, it
> is here where I call the ReleaseComObject
>
> For the same .Net method. One is called by VC++ client, I only need
> to call ReleaseComObject once, but for the VB client I have to call
> ReleaseComObject 3 times before the object is release
>
> If I keep calling ReleaseComObject until the return value is 0, then
> I will get an exception
> "COM object that has been separated from its underlying RCW can not
> be used."
>
> That got me really worried , why 3 times ? Is it possible for me to
> get the exception by calling ReleaseComObject 3 times? (Because we
> have not control how the client is using our framework)
I don't think you should be calling ReleaseComObject three times. As a
matter of fact, you shouldn't be calling it at all in this case. If the
same object is going to be placed into the ArrayList, then you shouldn't be
calling ReleaseComObject on the object you take out, as it is going to
invalidate the wrapper that you are placing into the ArrayList in its place.
Basically, you should be releasing the object when you are done with it
(which you aren't in this case).
--
- Nicholas Paldino [.NET/C# MVP]
- mvp@spam.guard.caspershouse.com
>
> Please advice.
> Thanks so much for your help.
> John
>
> On May 15, 7:03 pm, "Nicholas Paldino [.NET/C# MVP]"
> <m...@spam.guard.caspershouse.com> wrote:
>> John,
>>
>> Regardless of version, you should be calling ReleaseComObject on
>> references to COM objects that you have when you are done with them. COM
>> depends on reference counting, and while garbage collection will
>> ultimately
>> take care of stray references that you have (and properly decrement the
>> reference count, which will ultimately handle the disposing of the COM
>> object that the Runtime Callable Wrapper holds on to), it isn't a good
>> idea
>> to not release the objects when you are done with them.
>>
>> In other words, don't remove the call in .NET 2.0 because you think
>> it
>> works.
>>
>> As for .NET 1.1, the ReleaseComObject method existed on the Marshal
>> class in that version of the framework, so there is no reason you can't
>> use
>> it there.
>>
>> --
>> - Nicholas Paldino [.NET/C# MVP]
>> - m...@spam.guard.caspershouse.com
>>
>> <john...@gmail.com> wrote in message
>>
>> news:1179280286.509480.83450@n59g2000hsh.googlegroups.com...
>>
>>
>>
>> > We have a project in .NET 1.1 , some of the .NET methods take COM
>> > interface reference pointer as a parameter, somehow we have to call
>> > Marshal.ReleaseComObject to release the COM Object, otherwise the COM
>> > object will never get release, Even we call gc.Collect()
>>
>> > But the same code compiles in .NET 2.0 works without the
>> > Marshal.ReleaseComObject. (Unfortunately the project is supposed to
>> > run on .NET 1.1.)
>>
>> > Is this a known problem? What is the remedy besides
>> > Marshal.ReleaseComObject? (We know it is dangerous to call
>> > Marshal.ReleaseComObject since we do not have total control of the
>> > COM
>> > interface pointer )
>>
>> > Thanks in advance.
>> > John- Hide quoted text -
>>
>> - Show quoted text -
>
>