How to try something repeatedly using try-catch?

[Ed Staffin]

Hi,
In vb6, if I had an error handler I could catch an error,
make a correction and then try it again using resume. I
want to do the same thing in vb.net.

I am trying to deal with some concurrency issues. I want
to be able to catch a error, wait a few milliseconds and
then try it again. Any help on this would be great.
Thanks ... Ed

[Andy Gaskell]

Do you want to try again once? X times? Keep trying forever?

"Ed Staffin" <an*******@discussions.microsoft.com> wrote in message
news:b1****************************@phx.gbl...

Hi,
In vb6, if I had an error handler I could catch an error,
make a correction and then try it again using resume. I
want to do the same thing in vb.net.

I am trying to deal with some concurrency issues. I want
to be able to catch a error, wait a few milliseconds and
then try it again. Any help on this would be great.
Thanks ... Ed

[Al Reid]

Perhaps with some embellishment, something like this may work:

Dim blnSuccess As Boolean

Do Until blnSuccess
Try
... 'Whatever needs to be done
blnSuccess = True
Catch e as exception
.... If it is the error you think you can retry then wait
End Try
Loop
--
Al Reid

"It ain't what you don't know that gets you into trouble. It's what you know
for sure that just ain't so." --- Mark Twain

"Ed Staffin" <an*******@discussions.microsoft.com> wrote in message news:b1****************************@phx.gbl...

Hi,
In vb6, if I had an error handler I could catch an error,
make a correction and then try it again using resume. I
want to do the same thing in vb.net.

I am trying to deal with some concurrency issues. I want
to be able to catch a error, wait a few milliseconds and
then try it again. Any help on this would be great.
Thanks ... Ed

[Jay B. Harlow [MVP - Outlook]]

Ed,
In addition to the Loop that Al showed, you can use Goto within a Catch
block to go to a label in the Try Block.

In this instance I consider Goto more of a Resume Try than an actual Goto.
;-)

Try
TryAgain:
... 'Whatever needs to be done
Catch e as exception
.... If it is the error you think you can retry then wait
Goto TryAgain
End Try

Normally I put an If around the "Resume Try" (goto) so as to avoid an
endless loop.

Something like:
Try
TryAgain:
AttemptToReadFile()
' Throw New System.IO.FileNotFoundException
Catch ex As System.IO.FileNotFoundException
If MessageBox.Show("What would you like to do?", "File not
found", MessageBoxButtons.RetryCancel, MessageBoxIcon.Question,
MessageBoxDefaultButton.Button2) = DialogResult.Retry Then
GoTo TryAgain
Else
Throw ' let error propagate up
End If
End Try

Hope this helps
Jay

"Ed Staffin" <an*******@discussions.microsoft.com> wrote in message
news:b1****************************@phx.gbl...

Hi,
In vb6, if I had an error handler I could catch an error,
make a correction and then try it again using resume. I
want to do the same thing in vb.net.

I am trying to deal with some concurrency issues. I want
to be able to catch a error, wait a few milliseconds and
then try it again. Any help on this would be great.
Thanks ... Ed

[Al Reid]

Jay,

Somehow, the use of the "GoTo" statement just doesn't ever seem to come to mind as a solution unless I am *really* stuck and can
find no other way out. For others, it seems to be the first and only choice.

To each his own.

--
Al Reid

"It ain't what you don't know that gets you into trouble. It's what you know
for sure that just ain't so." --- Mark Twain

"Jay B. Harlow [MVP - Outlook]" <Ja************@msn.com> wrote in message news:ue****************@TK2MSFTNGP09.phx.gbl...

Ed,
In addition to the Loop that Al showed, you can use Goto within a Catch
block to go to a label in the Try Block.

In this instance I consider Goto more of a Resume Try than an actual Goto.
;-)

Try
TryAgain:
... 'Whatever needs to be done
Catch e as exception
.... If it is the error you think you can retry then wait
Goto TryAgain
End Try

Normally I put an If around the "Resume Try" (goto) so as to avoid an
endless loop.

Something like:
Try
TryAgain:
AttemptToReadFile()
' Throw New System.IO.FileNotFoundException
Catch ex As System.IO.FileNotFoundException
If MessageBox.Show("What would you like to do?", "File not
found", MessageBoxButtons.RetryCancel, MessageBoxIcon.Question,
MessageBoxDefaultButton.Button2) = DialogResult.Retry Then
GoTo TryAgain
Else
Throw ' let error propagate up
End If
End Try

Hope this helps
Jay

"Ed Staffin" <an*******@discussions.microsoft.com> wrote in message
news:b1****************************@phx.gbl...

Hi,
In vb6, if I had an error handler I could catch an error,
make a correction and then try it again using resume. I
want to do the same thing in vb.net.

I am trying to deal with some concurrency issues. I want
to be able to catch a error, wait a few milliseconds and
then try it again. Any help on this would be great.
Thanks ... Ed

[Robin Tucker]

Something like this might work ok......

Dim bDone as boolean = false

Do
Try
.......
.......
.......

bDone = true

catch Ex as Exception

End Try

loop while not bDone

"Ed Staffin" <an*******@discussions.microsoft.com> wrote in message
news:b1****************************@phx.gbl...

Hi,
In vb6, if I had an error handler I could catch an error,
make a correction and then try it again using resume. I
want to do the same thing in vb.net.

I am trying to deal with some concurrency issues. I want
to be able to catch a error, wait a few milliseconds and
then try it again. Any help on this would be great.
Thanks ... Ed

[Cor Ligthert]

Hi Ed,

I have nothing to add to that nice compact code from Al (or Robin), however
when you are doing that, did you also have already seen this rollback, when
you do not do something like this or in another way, I think that you will
get with a dataset strange behaviour.

http://support.microsoft.com/default...b;en-us;310351

Cor

[DareDevil]

This code will give you a specified number of attempts to handle an exception..

Dim retries As Long = 3 'number of attempts before rethrowing to an outer level
Tr
retry:
retries -=
'normal code to execut
Catch ex As Exceptio
If (retries >= 0)
'Rectify problem..
GoTo retr
Else 'rethrow the exact same exception..
Throw e
End I
End Try

[Chris Dunaway]

On Tue, 11 May 2004 08:02:38 -0500, Jay B. Harlow [MVP - Outlook] wrote:

Ed,
In addition to the Loop that Al showed, you can use Goto within a Catch
block to go to a label in the Try Block.

Jay, is there any reason to put the label *inside* the Try instead of
outside it? Does it make any difference?

Try
TryAgain:
'Whatever
Catch
If SomeCondition Then
Goto TryAgain
EndIf
End Try
As opposed to this:

TryAgain:
Try
'Whatever
Catch
If SomeCondition Then
Goto TryAgain
EndIf
End Try
In this instance I consider Goto more of a Resume Try than an actual Goto.
;-)

I think adding a ReTry keyword would be nice, but like you said you'd have
to watch out for an endless loop. Perhaps the ReTry could have optional
parameters to prevent that:

ReTry [[MaxRetries][,RetryDelayMs]]

Just a thought
--
Chris

To send me an E-mail, remove the "[", "]", underscores ,lunchmeat, and
replace certain words in my E-Mail address.

[Jay B. Harlow [MVP - Outlook]]

Al,
Unfortunately too many people feel that bad use of a Goto makes the Goto
bad.

I feel "correctness" is more important then any preconceived notions I may
have had about bad uses of Goto in the past.

Of course "correctness" is subjective.

Hope this helps
Jay

"Al Reid" <ar*****@reidDASHhome.com> wrote in message
news:%2****************@TK2MSFTNGP12.phx.gbl...

Jay,

Somehow, the use of the "GoTo" statement just doesn't ever seem to come to mind as a solution unless I am *really* stuck and can find no other way out. For others, it seems to be the first and only choice.
To each his own.

--
Al Reid

"It ain't what you don't know that gets you into trouble. It's what you know for sure that just ain't so." --- Mark Twain

"Jay B. Harlow [MVP - Outlook]" <Ja************@msn.com> wrote in message

news:ue****************@TK2MSFTNGP09.phx.gbl...

Ed,
In addition to the Loop that Al showed, you can use Goto within a Catch
block to go to a label in the Try Block.

In this instance I consider Goto more of a Resume Try than an actual Goto. ;-)

Try
TryAgain:
... 'Whatever needs to be done
Catch e as exception
.... If it is the error you think you can retry then wait
Goto TryAgain
End Try

Normally I put an If around the "Resume Try" (goto) so as to avoid an
endless loop.

Something like:
Try
TryAgain:
AttemptToReadFile()
' Throw New System.IO.FileNotFoundException
Catch ex As System.IO.FileNotFoundException
If MessageBox.Show("What would you like to do?", "File not
found", MessageBoxButtons.RetryCancel, MessageBoxIcon.Question,
MessageBoxDefaultButton.Button2) = DialogResult.Retry Then
GoTo TryAgain
Else
Throw ' let error propagate up
End If
End Try

Hope this helps
Jay

"Ed Staffin" <an*******@discussions.microsoft.com> wrote in message
news:b1****************************@phx.gbl...

Hi,
In vb6, if I had an error handler I could catch an error,
make a correction and then try it again using resume. I
want to do the same thing in vb.net.

I am trying to deal with some concurrency issues. I want
to be able to catch a error, wait a few milliseconds and
then try it again. Any help on this would be great.
Thanks ... Ed