Dispose then set to nothing

**=?UTF-8?B?R8O2cmFuIEFuZGVyc3Nvbg==?=** · Feb 27 '07, 01:15 AM

Re: Dispose then set to nothing

Hao Jiang wrote:

Hi,
>
I see in many MS example code that looks like this
>
Public Sub Foo()
dim myCustomer as New Customer
...
myCustomer.Disp ose()
myCustomer = Nothing
End Sub
>
I'm wondering if setting myCustomer = Nothing is necessary in this case?
Since myCustomer is a private variable, once it goes out of scope at the next
line, the reference to the object should be released.
>
Thanks.
>
Hao

That is correct. Removing the reference is pointless in this case.

--
GÃ¶ran Andersson
_____

guffa.com

http://www.guffa.com

Göran Anderssons privata hemsida.

**Herfried K. Wagner [MVP]** · Feb 27 '07, 02:05 AM

Re: Dispose then set to nothing

"Hao Jiang" <Hao Jiang@discussio ns.microsoft.co mschrieb:

Public Sub Foo()
dim myCustomer as New Customer
...
myCustomer.Disp ose()
myCustomer = Nothing
End Sub
>
I'm wondering if setting myCustomer = Nothing is necessary in this case?

No, it actually isn't necessary for the reason you mentioned.

--
M S Herfried K. Wagner
M V P <URL:http://dotnet.mvps.org/>
V B <URL:http://dotnet.mvps.org/dotnet/faqs/>

**Jay B. Harlow [MVP - Outlook]** · Feb 27 '07, 03:55 AM

Re: Dispose then set to nothing

Hao Jiang,
As GÃ¶ran & Herfried suggests setting myCustomer = Nothing is not needed for
the reason you give.

Instead of calling Dispose outright I would recommend using the new Using
statement in .NET 2.0 (VS 2005). The Using statement ensures that Dispose is
called even if one of the statements contained by the Using throws an
exception.

Public Sub Foo()

Using myCustomer as New Customer

...

End Using

End Sub

Which is basically the following in .NET 1.x:

Dim myCustomer As New Customer
Try
DoSomething()
Finally
If myCustomer IsNot Nothing Then
myCustomer.Disp ose()
End If
End Try

--
Hope this helps
Jay B. Harlow [MVP - Outlook]
..NET Application Architect, Enthusiast, & Evangelist
T.S. Bradley - http://www.tsbradley.net

"Hao Jiang" <Hao Jiang@discussio ns.microsoft.co mwrote in message
news:4551F173-DAB8-4F74-AE61-9F4298362B17@mi crosoft.com...

Hi,
>
I see in many MS example code that looks like this
>
Public Sub Foo()
dim myCustomer as New Customer
...
myCustomer.Disp ose()
myCustomer = Nothing
End Sub
>
I'm wondering if setting myCustomer = Nothing is necessary in this case?
Since myCustomer is a private variable, once it goes out of scope at the
next
line, the reference to the object should be released.
>
Thanks.
>
Hao

**Cor Ligthert [MVP]** · Feb 27 '07, 05:55 AM

Re: Dispose then set to nothing

Hao Jiang,

Do you mean with MS samples, samples made by Micrsoft, if so can you than
show us some of those?
(URL's)

Because it is not correct, it is as
dim a as integer = 1 + 1
if a <2 then messagebox.show "there was a calculation error"

Thanks in advance,

Cor

"Jay B. Harlow [MVP - Outlook]" <Jay_Harlow_MVP @tsbradley.nets chreef in
bericht news:eItOnFiWHH A.4860@TK2MSFTN GP04.phx.gbl...

Hao Jiang,
As Göran & Herfried suggests setting myCustomer = Nothing is not needed
for the reason you give.
>
Instead of calling Dispose outright I would recommend using the new Using
statement in .NET 2.0 (VS 2005). The Using statement ensures that Dispose
is called even if one of the statements contained by the Using throws an
exception.
>

>Public Sub Foo()

Using myCustomer as New Customer

> ...

End Using

>End Sub

>
Which is basically the following in .NET 1.x:
>
Dim myCustomer As New Customer
Try
DoSomething()
Finally
If myCustomer IsNot Nothing Then
myCustomer.Disp ose()
End If
End Try
>
--
Hope this helps
Jay B. Harlow [MVP - Outlook]
.NET Application Architect, Enthusiast, & Evangelist
T.S. Bradley - http://www.tsbradley.net
>
>
"Hao Jiang" <Hao Jiang@discussio ns.microsoft.co mwrote in message
news:4551F173-DAB8-4F74-AE61-9F4298362B17@mi crosoft.com...

>Hi,
>>
>I see in many MS example code that looks like this
>>
>Public Sub Foo()
> dim myCustomer as New Customer
> ...
> myCustomer.Disp ose()
> myCustomer = Nothing
>End Sub
>>
>I'm wondering if setting myCustomer = Nothing is necessary in this case?
>Since myCustomer is a private variable, once it goes out of scope at the
>next
>line, the reference to the object should be released.
>>
>Thanks.
>>
>Hao

>

**aaron.kempf@gmail.com** · Feb 27 '07, 05:05 PM

Re: Dispose then set to nothing

yeah; in vb6 when a variable went out of scope; it automagically
cleaned up after itself

except for DAO-- (which MS just ressurrected)

On Feb 26, 3:30 pm, Hao Jiang <Hao J...@discussion s.microsoft.com >
wrote:

Hi,
>
I see in many MS example code that looks like this
>
Public Sub Foo()
dim myCustomer as New Customer
...
myCustomer.Disp ose()
myCustomer = Nothing
End Sub
>
I'm wondering if setting myCustomer = Nothing is necessary in this case?
Since myCustomer is a private variable, once it goes out of scope at the next
line, the reference to the object should be released.
>
Thanks.
>
Hao

**=?Utf-8?B?SGFvIEppYW5n?=** · Feb 27 '07, 05:35 PM

Re: Dispose then set to nothing

Thanks Goran, Hefried and Jay! That's what I thought.

Cor, please check out the 2nd and 3rd code section on this MS page:

Error - Office.com - Microsoft Support

http://support.microsoft.com/kb/888168

Hao

"Cor Ligthert [MVP]" wrote:

Hao Jiang,
>
Do you mean with MS samples, samples made by Micrsoft, if so can you than
show us some of those?
(URL's)
>
Because it is not correct, it is as
dim a as integer = 1 + 1
if a <2 then messagebox.show "there was a calculation error"
>
Thanks in advance,
>
Cor
>
"Jay B. Harlow [MVP - Outlook]" <Jay_Harlow_MVP @tsbradley.nets chreef in
bericht news:eItOnFiWHH A.4860@TK2MSFTN GP04.phx.gbl...

Hao Jiang,
As GÃ¶ran & Herfried suggests setting myCustomer = Nothing is not needed
for the reason you give.

Instead of calling Dispose outright I would recommend using the new Using
statement in .NET 2.0 (VS 2005). The Using statement ensures that Dispose
is called even if one of the statements contained by the Using throws an
exception.

Public Sub Foo()

Using myCustomer as New Customer

...

End Using

End Sub

Which is basically the following in .NET 1.x:

Dim myCustomer As New Customer
Try
DoSomething()
Finally
If myCustomer IsNot Nothing Then
myCustomer.Disp ose()
End If
End Try

--
Hope this helps
Jay B. Harlow [MVP - Outlook]
.NET Application Architect, Enthusiast, & Evangelist
T.S. Bradley - http://www.tsbradley.net

"Hao Jiang" <Hao Jiang@discussio ns.microsoft.co mwrote in message
news:4551F173-DAB8-4F74-AE61-9F4298362B17@mi crosoft.com...

Hi,
>
I see in many MS example code that looks like this
>
Public Sub Foo()
dim myCustomer as New Customer
...
myCustomer.Disp ose()
myCustomer = Nothing
End Sub
>
I'm wondering if setting myCustomer = Nothing is necessary in this case?
Since myCustomer is a private variable, once it goes out of scope at the
next
line, the reference to the object should be released.
>
Thanks.
>
Hao

>
>
>

**Brian Gideon** · Feb 27 '07, 05:45 PM

Re: Dispose then set to nothing

On Feb 26, 5:30 pm, Hao Jiang <Hao J...@discussion s.microsoft.com >
wrote:

Hi,
>
I see in many MS example code that looks like this
>
Public Sub Foo()
dim myCustomer as New Customer
...
myCustomer.Disp ose()
myCustomer = Nothing
End Sub
>
I'm wondering if setting myCustomer = Nothing is necessary in this case?
Since myCustomer is a private variable, once it goes out of scope at the next
line, the reference to the object should be released.
>
Thanks.
>
Hao

Hao,

To be absolutely precise the object is eligible for garbage collection
even before it goes out of scope as long as it's not used anymore. I
don't know how aggressive the GC rules are specifically, but it is
possible that the GC would consider the line myCustomer = Nothing as
having no side effects on the object and would collect the object even
before the line executed. I suppose it's reasonable to theorize that
the JIT compiler could optimize the line away as well.

Brian

Brian

**Brian Gideon** · Feb 27 '07, 05:45 PM

Re: Dispose then set to nothing

On Feb 27, 11:25 am, Hao Jiang <HaoJi...@discu ssions.microsof t.com>
wrote:

Thanks Goran, Hefried and Jay! That's what I thought.
>
Cor, please check out the 2nd and 3rd code section on this MS page:http://support.microsoft.com/kb/888168
>
Hao

Hmm...yeah, those are poorly written examples.

**Cor Ligthert [MVP]** · Feb 27 '07, 06:05 PM

Re: Dispose then set to nothing

Hao,

Thanks, I have sent it further

Cor

"Hao Jiang" <HaoJiang@discu ssions.microsof t.comschreef in bericht
news:FAA14219-133E-44F6-A858-B27760C9955B@mi crosoft.com...

Thanks Goran, Hefried and Jay! That's what I thought.
>
Cor, please check out the 2nd and 3rd code section on this MS page:

Error - Office.com - Microsoft Support

http://support.microsoft.com/kb/888168

>
Hao
>
"Cor Ligthert [MVP]" wrote:
>

>Hao Jiang,
>>
>Do you mean with MS samples, samples made by Micrsoft, if so can you than
>show us some of those?
>(URL's)
>>
>Because it is not correct, it is as
>dim a as integer = 1 + 1
>if a <2 then messagebox.show "there was a calculation error"
>>
>Thanks in advance,
>>
>Cor
>>
>"Jay B. Harlow [MVP - Outlook]" <Jay_Harlow_MVP @tsbradley.nets chreef in
>bericht news:eItOnFiWHH A.4860@TK2MSFTN GP04.phx.gbl...

Hao Jiang,
As Göran & Herfried suggests setting myCustomer = Nothing is not needed
for the reason you give.
>
Instead of calling Dispose outright I would recommend using the new
Using
statement in .NET 2.0 (VS 2005). The Using statement ensures that
Dispose
is called even if one of the statements contained by the Using throws
an
exception.
>
>Public Sub Foo()
Using myCustomer as New Customer
> ...
End Using
>End Sub
>
Which is basically the following in .NET 1.x:
>
Dim myCustomer As New Customer
Try
DoSomething()
Finally
If myCustomer IsNot Nothing Then
myCustomer.Disp ose()
End If
End Try
>
--
Hope this helps
Jay B. Harlow [MVP - Outlook]
.NET Application Architect, Enthusiast, & Evangelist
T.S. Bradley - http://www.tsbradley.net
>
>
"Hao Jiang" <Hao Jiang@discussio ns.microsoft.co mwrote in message
news:4551F173-DAB8-4F74-AE61-9F4298362B17@mi crosoft.com...
>Hi,
>>
>I see in many MS example code that looks like this
>>
>Public Sub Foo()
> dim myCustomer as New Customer
> ...
> myCustomer.Disp ose()
> myCustomer = Nothing
>End Sub
>>
>I'm wondering if setting myCustomer = Nothing is necessary in this
>case?
>Since myCustomer is a private variable, once it goes out of scope at
>the
>next
>line, the reference to the object should be released.
>>
>Thanks.
>>
>Hao
>

>>
>>
>>

**Cor Ligthert [MVP]** · Feb 27 '07, 06:15 PM

Re: Dispose then set to nothing

Brian,

It is completely inside the method, if the dispose is not there it goes out
of scoop and will be disposed because the method ends.

In my idea it is completely out of sense. (Not that I have the idea that you
have an opposite opinion).

Cor

"Brian Gideon" <briangideon@ya hoo.comschreef in bericht
news:1172597399 .940193.16580@h 3g2000cwc.googl egroups.com...

On Feb 26, 5:30 pm, Hao Jiang <Hao J...@discussion s.microsoft.com >
wrote:

>Hi,
>>
>I see in many MS example code that looks like this
>>
>Public Sub Foo()
> dim myCustomer as New Customer
> ...
> myCustomer.Disp ose()
> myCustomer = Nothing
>End Sub
>>
>I'm wondering if setting myCustomer = Nothing is necessary in this case?
>Since myCustomer is a private variable, once it goes out of scope at the
>next
>line, the reference to the object should be released.
>>
>Thanks.
>>
>Hao

>
Hao,
>
To be absolutely precise the object is eligible for garbage collection
even before it goes out of scope as long as it's not used anymore. I
don't know how aggressive the GC rules are specifically, but it is
possible that the GC would consider the line myCustomer = Nothing as
having no side effects on the object and would collect the object even
before the line executed. I suppose it's reasonable to theorize that
the JIT compiler could optimize the line away as well.
>
Brian
>
Brian
>
>

**Brian Gideon** · Feb 27 '07, 06:35 PM

Re: Dispose then set to nothing

On Feb 27, 12:00 pm, "Cor Ligthert [MVP]" <notmyfirstn... @planet.nl>
wrote:

Brian,
>
It is completely inside the method, if the dispose is not there it goes out
of scoop and will be disposed because the method ends.
>
In my idea it is completely out of sense. (Not that I have the idea that you
have an opposite opinion).
>
Cor

I'm not seeing how that's relevant. What I'm saying is that the
object is eligible for collection before the method returns and
possibly before it's variable reference is set to Nothing. And if
that's not true now then there's nothing in the CLI specification that
says a future version can't be that aggressive. Not only is setting
the reference to Nothing unnecessary, it could actually occur *after*
the memory has been released. That's something to consider in the
context of the OP's question.

**=?ISO-8859-1?Q?G=F6ran_Andersson?=** · Feb 27 '07, 07:05 PM

Re: Dispose then set to nothing

Cor Ligthert [MVP] wrote:

It is completely inside the method, if the dispose is not there it goes out
of scoop and will be disposed because the method ends.

Just to be sure that it doesn't add to the confusion:

Removing the reference to an object and disposing an object are two
completely different things.

--
Göran Andersson
_____

guffa.com

http://www.guffa.com

Göran Anderssons privata hemsida.

**Cor Ligthert [MVP]** · Feb 27 '07, 09:25 PM

Re: Dispose then set to nothing

Removing the reference to an object and disposing an object are two

completely different things.

Yes going to the toilet and flush the toilet too, but here is an automatic
flushing system, a little bit strange to do it twice.

Cor,

"Göran Andersson" <guffa@guffa.co mschreef in bericht
news:%23S2Em%23 pWHHA.392@TK2MS FTNGP06.phx.gbl ...

Cor Ligthert [MVP] wrote:

>It is completely inside the method, if the dispose is not there it goes
>out of scoop and will be disposed because the method ends.

>
Just to be sure that it doesn't add to the confusion:
>
Removing the reference to an object and disposing an object are two
completely different things.
>
--
Göran Andersson
_____
http://www.guffa.com

**Brian Gideon** · Feb 27 '07, 09:45 PM

Re: Dispose then set to nothing

On Feb 27, 3:17 pm, "Cor Ligthert [MVP]" <notmyfirstn... @planet.nl>
wrote:

Yes going to the toilet and flush the toilet too, but here is an automatic
flushing system, a little bit strange to do it twice.
>
Cor,
>

Cor,

I'm apologize in advance, I'm having a hard time understanding what
you're saying. How does your analogy relate to .NET. What's
happening twice? And how does the concept of disposing an object
relate to the OP's question?

To me anyway, the fact that the OP's question just happened to involve
an object that implements IDisposable was completely irrelevant.

Brian

Dispose then set to nothing

Dispose then set to nothing

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