scope of command and garbage collection

**Herfried K. Wagner [MVP]** · May 24 '06, 12:55 PM

Re: scope of command and garbage collection

"Smokey Grindle" <nospamhere@don tspam.net> schrieb:[color=blue]
> Say I have the following piece of code
>
> Dim dtPerson As New DataTable
> Dim cmd As New SqlClient.SqlCo mmand("sp_test" , database)
> dtPerson.Load(c md.ExecuteReade r)
> cmd.dispose()
>
> which instanciates the command object, uses it then destroys it, now if i
> rewrote it like this
>
> Dim dtPerson As New DataTable
> dtPerson.Load(N ew SqlClient.SqlCo mmand("test", database)
>
> would that still act the same? because the commands scope is inside the
> load method, shouldnt it be destroyed after the point of execution has
> passed the load method?[/color]

No, it won't. It will be destoyed by the garbage collector later, but there
is no guarantee that it gets destroyed immediately.

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

**Jay B. Harlow [MVP - Outlook]** · May 24 '06, 01:05 PM

Re: scope of command and garbage collection

Smokey,
Addition to Herfried's comments.

In .NET 2.0 I would recommend:

| Dim dtPerson As New DataTable
Using cmd As New SqlClient.SqlCo mmand("sp_test" , database)
| dtPerson.Load(c md.ExecuteReade r)
End Using

If .NET 1.x I would recommend:

| Dim dtPerson As New DataTable
| Dim cmd As New SqlClient.SqlCo mmand("sp_test" , database)
Try
| dtPerson.Load(c md.ExecuteReade r)
Finally
| cmd.dispose()
End Try

This ensures that the SqlCommand is disposed of even if the DataTable.Load
method itself threw an exception.

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

"Smokey Grindle" <nospamhere@don tspam.net> wrote in message
news:eOBMA7yfGH A.5088@TK2MSFTN GP02.phx.gbl...
| Say I have the following piece of code
|
| Dim dtPerson As New DataTable
| Dim cmd As New SqlClient.SqlCo mmand("sp_test" , database)
| dtPerson.Load(c md.ExecuteReade r)
| cmd.dispose()
|
| which instanciates the command object, uses it then destroys it, now if i
| rewrote it like this
|
| Dim dtPerson As New DataTable
| dtPerson.Load(N ew SqlClient.SqlCo mmand("test", database)
|
| would that still act the same? because the commands scope is inside the
load
| method, shouldnt it be destroyed after the point of execution has passed
the
| load method? basicly creating a command that destroys itself after
| execution? or is it better not to do it this way because that is not how
it
| works?
|
|

**Smokey Grindle** · May 24 '06, 01:15 PM

Re: scope of command and garbage collection

Yes, I was also looking at USING.

thanks both

"Jay B. Harlow [MVP - Outlook]" <Jay_Harlow_MVP @tsbradley.net> wrote in
message news:eJEJTKzfGH A.2208@TK2MSFTN GP05.phx.gbl...[color=blue]
> Smokey,
> Addition to Herfried's comments.
>
> In .NET 2.0 I would recommend:
>
> | Dim dtPerson As New DataTable
> Using cmd As New SqlClient.SqlCo mmand("sp_test" , database)
> | dtPerson.Load(c md.ExecuteReade r)
> End Using
>
> If .NET 1.x I would recommend:
>
> | Dim dtPerson As New DataTable
> | Dim cmd As New SqlClient.SqlCo mmand("sp_test" , database)
> Try
> | dtPerson.Load(c md.ExecuteReade r)
> Finally
> | cmd.dispose()
> End Try
>
> This ensures that the SqlCommand is disposed of even if the DataTable.Load
> method itself threw an exception.
>
> --
> Hope this helps
> Jay B. Harlow [MVP - Outlook]
> .NET Application Architect, Enthusiast, & Evangelist
> T.S. Bradley - http://www.tsbradley.net
>
>
> "Smokey Grindle" <nospamhere@don tspam.net> wrote in message
> news:eOBMA7yfGH A.5088@TK2MSFTN GP02.phx.gbl...
> | Say I have the following piece of code
> |
> | Dim dtPerson As New DataTable
> | Dim cmd As New SqlClient.SqlCo mmand("sp_test" , database)
> | dtPerson.Load(c md.ExecuteReade r)
> | cmd.dispose()
> |
> | which instanciates the command object, uses it then destroys it, now if
> i
> | rewrote it like this
> |
> | Dim dtPerson As New DataTable
> | dtPerson.Load(N ew SqlClient.SqlCo mmand("test", database)
> |
> | would that still act the same? because the commands scope is inside the
> load
> | method, shouldnt it be destroyed after the point of execution has passed
> the
> | load method? basicly creating a command that destroys itself after
> | execution? or is it better not to do it this way because that is not how
> it
> | works?
> |
> |
>
>[/color]

**Robin Mark Tucker** · May 24 '06, 01:15 PM

Re: scope of command and garbage collection

Hi Jay,

Can you explain a little more about the difference between the Using in .NET
2.0 and the .NET 1.1 version of the code? I am new to .NET 2.0, but quite
experienced with .NET 1.1. I had mostly used the Try/Catch method, but I'm
thinking .NET 2.0 wraps a hidden exception handler around the Using
statement for just such eventualities. Is there an MSDN document about
this?

Thanks,

Robin

"Jay B. Harlow [MVP - Outlook]" <Jay_Harlow_MVP @tsbradley.net> wrote in
message news:eJEJTKzfGH A.2208@TK2MSFTN GP05.phx.gbl...[color=blue]
> Smokey,
> Addition to Herfried's comments.
>
> In .NET 2.0 I would recommend:
>
> | Dim dtPerson As New DataTable
> Using cmd As New SqlClient.SqlCo mmand("sp_test" , database)
> | dtPerson.Load(c md.ExecuteReade r)
> End Using
>
> If .NET 1.x I would recommend:
>
> | Dim dtPerson As New DataTable
> | Dim cmd As New SqlClient.SqlCo mmand("sp_test" , database)
> Try
> | dtPerson.Load(c md.ExecuteReade r)
> Finally
> | cmd.dispose()
> End Try
>
> This ensures that the SqlCommand is disposed of even if the DataTable.Load
> method itself threw an exception.
>
> --
> Hope this helps
> Jay B. Harlow [MVP - Outlook]
> .NET Application Architect, Enthusiast, & Evangelist
> T.S. Bradley - http://www.tsbradley.net
>
>
> "Smokey Grindle" <nospamhere@don tspam.net> wrote in message
> news:eOBMA7yfGH A.5088@TK2MSFTN GP02.phx.gbl...
> | Say I have the following piece of code
> |
> | Dim dtPerson As New DataTable
> | Dim cmd As New SqlClient.SqlCo mmand("sp_test" , database)
> | dtPerson.Load(c md.ExecuteReade r)
> | cmd.dispose()
> |
> | which instanciates the command object, uses it then destroys it, now if
> i
> | rewrote it like this
> |
> | Dim dtPerson As New DataTable
> | dtPerson.Load(N ew SqlClient.SqlCo mmand("test", database)
> |
> | would that still act the same? because the commands scope is inside the
> load
> | method, shouldnt it be destroyed after the point of execution has passed
> the
> | load method? basicly creating a command that destroys itself after
> | execution? or is it better not to do it this way because that is not how
> it
> | works?
> |
> |
>
>[/color]

**Cor Ligthert [MVP]** · May 24 '06, 05:05 PM

Re: scope of command and garbage collection

Jay,

I would not use "using" without global exception handling or without forcing
the errors to the datarow.rowerro r property.

I know that you use probably the first and I the last, however in my opinion
is it good to explain that.

Cor

**Jay B. Harlow [MVP - Outlook]** · May 25 '06, 12:15 AM

Re: scope of command and garbage collection

Cor,
Agree, using (no pun intended) a global exception handler is a good idea
along with appropriate "local" error handling if appropriate.

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

"Cor Ligthert [MVP]" <notmyfirstname @planet.nl> wrote in message
news:%23GVZjO1f GHA.4940@TK2MSF TNGP05.phx.gbl. ..
| Jay,
|
| I would not use "using" without global exception handling or without
forcing
| the errors to the datarow.rowerro r property.
|
| I know that you use probably the first and I the last, however in my
opinion
| is it good to explain that.
|
| Cor
|
|

**Jay B. Harlow [MVP - Outlook]** · May 25 '06, 12:15 AM

Re: scope of command and garbage collection

Robin,
The Using statement is effectively:

Dim dtPerson As New DataTable

Using cmd As New SqlClient.SqlCo mmand("sp_test" , database)
+ Dim cmd As New SqlClient.SqlCo mmand("sp_test" , database)
+ Try
dtPerson.Load(c md.ExecuteReade r)
End Using
+ Finally
+ If cmd IsNot Nothing
+ cmd.dispose()
+ End If
+End Try

Where the lines marked with + are what VB creates in the IL. You can use
ILDASM to see specifically what VB does.

The IsNot Nothing is there to allow for the case where cmd is set to nothing
within the Using block.

For details of the new statement see:

http://msdn2.microsoft.com/en-US/library/htd05whh.aspx

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

"Robin Mark Tucker" <robintuckerhom e@removehotmail .comremove> wrote in
message news:e51m7d$jl1 $1$8302bc10@new s.demon.co.uk.. .
|
| Hi Jay,
|
| Can you explain a little more about the difference between the Using in
..NET
| 2.0 and the .NET 1.1 version of the code? I am new to .NET 2.0, but quite
| experienced with .NET 1.1. I had mostly used the Try/Catch method, but
I'm
| thinking .NET 2.0 wraps a hidden exception handler around the Using
| statement for just such eventualities. Is there an MSDN document about
| this?
|
| Thanks,
|
|
| Robin
|
| "Jay B. Harlow [MVP - Outlook]" <Jay_Harlow_MVP @tsbradley.net> wrote in
| message news:eJEJTKzfGH A.2208@TK2MSFTN GP05.phx.gbl...
| > Smokey,
| > Addition to Herfried's comments.
| >
| > In .NET 2.0 I would recommend:
| >
| > | Dim dtPerson As New DataTable
| > Using cmd As New SqlClient.SqlCo mmand("sp_test" , database)
| > | dtPerson.Load(c md.ExecuteReade r)
| > End Using
| >
| > If .NET 1.x I would recommend:
| >
| > | Dim dtPerson As New DataTable
| > | Dim cmd As New SqlClient.SqlCo mmand("sp_test" , database)
| > Try
| > | dtPerson.Load(c md.ExecuteReade r)
| > Finally
| > | cmd.dispose()
| > End Try
| >
| > This ensures that the SqlCommand is disposed of even if the
DataTable.Load
| > method itself threw an exception.
| >
| > --
| > Hope this helps
| > Jay B. Harlow [MVP - Outlook]
| > .NET Application Architect, Enthusiast, & Evangelist
| > T.S. Bradley - http://www.tsbradley.net
| >
| >
| > "Smokey Grindle" <nospamhere@don tspam.net> wrote in message
| > news:eOBMA7yfGH A.5088@TK2MSFTN GP02.phx.gbl...
| > | Say I have the following piece of code
| > |
| > | Dim dtPerson As New DataTable
| > | Dim cmd As New SqlClient.SqlCo mmand("sp_test" , database)
| > | dtPerson.Load(c md.ExecuteReade r)
| > | cmd.dispose()
| > |
| > | which instanciates the command object, uses it then destroys it, now
if
| > i
| > | rewrote it like this
| > |
| > | Dim dtPerson As New DataTable
| > | dtPerson.Load(N ew SqlClient.SqlCo mmand("test", database)
| > |
| > | would that still act the same? because the commands scope is inside
the
| > load
| > | method, shouldnt it be destroyed after the point of execution has
passed
| > the
| > | load method? basicly creating a command that destroys itself after
| > | execution? or is it better not to do it this way because that is not
how
| > it
| > | works?
| > |
| > |
| >
| >
|
|

scope of command and garbage collection

scope of command and garbage collection

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