Thread safe TextWriter question

fniles

Is this the correct syntax to make a Textwriter thread safe ? Thank you.

Dim swError As TextWriter
Dim swErrorSync As TextWriter
swError = New StreamWriter(Application.StartupPath & "\Log.txt", True)
swErrorSync = swError.Synchronized(swError)
swError.Write(Now & vbCrLf)
swError.Close()

Jul 31 '06 #1

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David Browne

"fniles" <fn****@pfmail.comwrote in message
news:Ou**************@TK2MSFTNGP03.phx.gbl...

Is this the correct syntax to make a Textwriter thread safe ? Thank you.

Dim swError As TextWriter
Dim swErrorSync As TextWriter
swError = New StreamWriter(Application.StartupPath & "\Log.txt", True)
swErrorSync = swError.Synchronized(swError)
swError.Write(Now & vbCrLf)
swError.Close()

No. Not quite. Threads should write to swErrorSync. And it's not clear
what code different threads are running. This snippet, as a whole, is
definitely not thread-safe.

David

Jul 31 '06 #2

fniles

I am sorry, I typed in incorrectly.
Pls tell me if the following is correct and thread safe.
Thanks.

Dim swError As TextWriter
Dim swErrorSync As TextWriter

swError = New StreamWriter(Application.StartupPath & "\Log.txt", True)
swErrorSync = swError.Synchronized(swError)
swErrorSync .Write(Now & vbCrLf)
swError.Close()
swErrorSync.Close()

"David Browne" <davidbaxterbrowne no potted me**@hotmail.comwrote in
message news:u%****************@TK2MSFTNGP03.phx.gbl...

>
"fniles" <fn****@pfmail.comwrote in message
news:Ou**************@TK2MSFTNGP03.phx.gbl...
>Is this the correct syntax to make a Textwriter thread safe ? Thank you.

Dim swError As TextWriter
Dim swErrorSync As TextWriter
swError = New StreamWriter(Application.StartupPath & "\Log.txt", True)
swErrorSync = swError.Synchronized(swError)
swError.Write(Now & vbCrLf)
swError.Close()

No. Not quite. Threads should write to swErrorSync. And it's not clear
what code different threads are running. This snippet, as a whole, is
definitely not thread-safe.

David

Jul 31 '06 #3

David Browne

"fniles" <fn****@pfmail.comwrote in message
news:uy*************@TK2MSFTNGP03.phx.gbl...

>I am sorry, I typed in incorrectly.
Pls tell me if the following is correct and thread safe.
Thanks.

Dim swError As TextWriter
Dim swErrorSync As TextWriter

swError = New StreamWriter(Application.StartupPath & "\Log.txt", True)
swErrorSync = swError.Synchronized(swError)
swErrorSync .Write(Now & vbCrLf)
swError.Close()
swErrorSync.Close()

No. That code is not thread-safe. If multiple threads execute that code
you will not necessarilly get correct, whole, ordered log entries.

If you refactored the code so that a single thread opened and closed the
file, while multiple threads accessed the syncronized StreamWriter wrapper,
then it would be.

David

Jul 31 '06 #4

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