Call the dispose method on a different thread if an exception is thrown

On 2003-10-15, Giovanni Bassi <gb****@coair.c om> wrote:

Hello Group,

I am running an operation in a different thread. There are resources that
are released when the thread is done running. This is done at the end of the
execution as it raises an event, and then the operation handling this event
calls threaded object's dispose method.
The problem is: If an exception is thrown the event is never raised, the
operation never executes dispose and my resources get stuck on the memory
until the app is finally closed and then, just then, the finalize method
will call the dispose method.
How can I know if an exception was thrown in a different thread? I need that
to be able to call the dispose method myself and not wait until finalize
runs whenever it feels like.

Thanks in advance for all the replies,

Giovanni Bassi

I think you may want to check into Try-Catch-Finally... The finally
block is always executed - even if an exception is thrown. I'm not
exactly sure with out seeing some code of course, but I would guess this
is a code structure issue. Is there any way you can post a scaled down
snippet of code that illustrates what you are trying to accomplish?

--
Tom Shelton
MVP [Visual Basic]

Hey Tom,

Thanks for the Reply.
Here is what is some code:
This runs on a menu click handler:

Dim objReports As Reports
objReports = New ExcelPayrollCD( strFullFileName ,
g_objTables.Con nection, intSerial)
AddHandler objReports.Repo rtFinished, AddressOf
objReports_Repo rtFinished

Dim objNewThreadSta rt As New Threading.Threa dStart(AddressO f
objReports.Gene rate)
Dim objNewThread As New Threading.Threa d(objNewThreadS tart)
objNewThread.St art()

And there is this sub to handle the above code:

Private Sub objReports_Repo rtFinished(ByVa l sender As Excel.Reports)

Dim Result As Excel.ReportRes ults
Result = sender.ReportRe sult

Dim objNewThreadSta rt As New Threading.Threa dStart(AddressO f
CType(sender, IDisposable).Di spose)
Dim objNewThread As New Threading.Threa d(objNewThreadS tart)
objNewThread.St art()

Select Case Result
Case Excel.ReportRes ults.OK
MessageBox.Show ("Report created!" & vbNewLine &
sender.FullFile Name & " saved.", "Payroll CD", MessageBoxButto ns.OK,
MessageBoxIcon. Information, MessageBoxDefau ltButton.Button 1)
Case Excel.ReportRes ults.Cancelled
MessageBox.Show ("Report cancelled.")
Case Excel.ReportRes ults.Connection TimeOut
MessageBox.Show ("Connection Timed Out.")
Case Excel.ReportRes ults.DataNotRet rived
MessageBox.Show ("Data Not Retrived.")
Case Excel.ReportRes ults.ReportMode lNotFound
MessageBox.Show ("Report model not found.")
Case Excel.ReportRes ults.UnknownErr or
MessageBox.Show ("Unkown Error.")
Case Else

End Select

End Sub
I want to catch an error on objReports.Gene rate, which is run at
objNewThread.St art.
Normally, without MultiThreading, I'd simply do:

Try
objReports.Gene rate()
Catch
'do whatever
Finally
objReports.Disp ose
End Try

but I can't because there is no direct call to objReports.Gene rate, and
objReports.Disp ose only runs when Sub objReports_Repo rtFinished gets called.

Any ideas?

Thanks again!
Giovanni Bassi

"Tom Shelton" <to*@mtogden.co m> wrote in message
news:ue******** *****@TK2MSFTNG P11.phx.gbl...

On 2003-10-15, Giovanni Bassi <gb****@coair.c om> wrote:

Hello Group,

I am running an operation in a different thread. There are resources that are released when the thread is done running. This is done at the end of the execution as it raises an event, and then the operation handling this event calls threaded object's dispose method.
The problem is: If an exception is thrown the event is never raised, the
operation never executes dispose and my resources get stuck on the memory until the app is finally closed and then, just then, the finalize method
will call the dispose method.
How can I know if an exception was thrown in a different thread? I need that to be able to call the dispose method myself and not wait until finalize
runs whenever it feels like.

Thanks in advance for all the replies,

Giovanni Bassi

I think you may want to check into Try-Catch-Finally... The finally
block is always executed - even if an exception is thrown. I'm not
exactly sure with out seeing some code of course, but I would guess this
is a code structure issue. Is there any way you can post a scaled down
snippet of code that illustrates what you are trying to accomplish?

--
Tom Shelton
MVP [Visual Basic]

On 2003-10-16, Giovanni Bassi <gb****@coair.c om> wrote:

Hey Tom,

Thanks for the Reply.
Here is what is some code:
This runs on a menu click handler:

Dim objReports As Reports
objReports = New ExcelPayrollCD( strFullFileName ,
g_objTables.Con nection, intSerial)
AddHandler objReports.Repo rtFinished, AddressOf
objReports_Repo rtFinished

Dim objNewThreadSta rt As New Threading.Threa dStart(AddressO f
objReports.Gene rate)
Dim objNewThread As New Threading.Threa d(objNewThreadS tart)
objNewThread.St art()

And there is this sub to handle the above code:

Private Sub objReports_Repo rtFinished(ByVa l sender As Excel.Reports)

Dim Result As Excel.ReportRes ults
Result = sender.ReportRe sult

Dim objNewThreadSta rt As New Threading.Threa dStart(AddressO f
CType(sender, IDisposable).Di spose)
Dim objNewThread As New Threading.Threa d(objNewThreadS tart)
objNewThread.St art()

Select Case Result
Case Excel.ReportRes ults.OK
MessageBox.Show ("Report created!" & vbNewLine &
sender.FullFile Name & " saved.", "Payroll CD", MessageBoxButto ns.OK,
MessageBoxIcon. Information, MessageBoxDefau ltButton.Button 1)
Case Excel.ReportRes ults.Cancelled
MessageBox.Show ("Report cancelled.")
Case Excel.ReportRes ults.Connection TimeOut
MessageBox.Show ("Connection Timed Out.")
Case Excel.ReportRes ults.DataNotRet rived
MessageBox.Show ("Data Not Retrived.")
Case Excel.ReportRes ults.ReportMode lNotFound
MessageBox.Show ("Report model not found.")
Case Excel.ReportRes ults.UnknownErr or
MessageBox.Show ("Unkown Error.")
Case Else

End Select

End Sub
I want to catch an error on objReports.Gene rate, which is run at
objNewThread.St art.
Normally, without MultiThreading, I'd simply do:

Try
objReports.Gene rate()
Catch
'do whatever
Finally
objReports.Disp ose
End Try

but I can't because there is no direct call to objReports.Gene rate, and
objReports.Disp ose only runs when Sub objReports_Repo rtFinished gets called.

Any ideas?

Thanks again!
Giovanni Bassi

Giovanni,

Looking over the code, assuming I understand what's happening :), I
would suggest you look into using an async delegate to call a method
that generates the report... I think you will save your self a lot of
trouble, and end up with the same results. Basically, what you would do
is create and call a method, called say GenerateReports , using async
delegate. The GenerateReports method would be as simple as:

Private Delegate Sub GenReportsDeleg ate()

' menu click...
Private Sub...
Dim async As New GenReportsDeleg ate(AddressOf Me.GenerateRepo rts)

' now call the method async like...
async.BeginInvo ke(AddressOf Me.GenerateRepo rtsComplete, Nothing)
End Sub

' Generate your reports in the background...
Private Sub GenerateReports ()
Dim objReports As Reports = _
New ExcelPayrollCD( strFullFileName , g_objTables.Con nection, intSerial)

AddHandler objReports.Repo rtFinished, AddressOf objReports_Repo rtFinished

Try
objReports.Gene rate()
Catch
' do whatever
Finally
objReports.Disp ose()
End Try
End Sub

' do this so you make sure EndInvoke is called
Private Sub GenerateReports Done(ByVal ar As IAsyncResult)
Dim async As GenReportsDeleg ate = _
DirectCast(ar.A syncState, GenReportsDeleg ate)

async.EndInvoke (ar)
End Sub

What will change, and I think for the better is that you will eliminate
all the explicit threading, since the system will manage the threads.
Not only that, in the end the code is simpler. I don't have the docs on
this machine to give you a reference in them, but you can find a pretty
good overview in the docs on MSDN...

http://msdn.microsoft.com/library/de...rogramming.asp

HTH
--
Tom Shelton
MVP [Visual Basic]