Multithreading Problem

1 May 2006 6:52 AM

Michael

Hi,

I am trying to create a multithreaded VB 2005 application which attempts to
create a new thread per Domain Controller (DC) in my environment. Each thread
connects to its allocated DC and enumerates all computer objects and extracts
the 'LastLogon' property. The results from each thread is then consolidated
so that I can get the true lastlogon date for each computer object.

However in my routine thats get actioned per thread, I have used the
following line which seems to halt each thread and doesn't progress to the
next line of code:

Dim searcher As New DirectorySearcher("LDAP://" + dc.Domain.ToString & "/" &
dc.Name)

Where dc is defined as ActiveDirectory.DomainController.

This is my method of connecting directly to a specific domain controller.
Why would this process halt when it works fine if I do not use
multithreading? Is there a better way of connecting directly to a domain
controller that would get around this problem?

Thanks,
Michael.

1 May 2006 12:17 PM

David Lee Conley

According to the DirectorySearcher class information in the help files:

Any public static (Shared in Visual Basic) members of this type are thread
safe. Any instance members are not guaranteed to be thread safe.

HTH

Dave

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"Michael" <Mich***@discussions.microsoft.com> wrote in message
news:9B4936F5-BEA0-48D4-B086-9415BB001735@microsoft.com...
> Hi,
>
> I am trying to create a multithreaded VB 2005 application which attempts
> to
> create a new thread per Domain Controller (DC) in my environment. Each
> thread
> connects to its allocated DC and enumerates all computer objects and
> extracts
> the 'LastLogon' property. The results from each thread is then
> consolidated
> so that I can get the true lastlogon date for each computer object.
>
> However in my routine thats get actioned per thread, I have used the
> following line which seems to halt each thread and doesn't progress to the
> next line of code:
>
>
> Dim searcher As New DirectorySearcher("LDAP://" + dc.Domain.ToString & "/"
> &
> dc.Name)
>
> Where dc is defined as ActiveDirectory.DomainController.
>
> This is my method of connecting directly to a specific domain controller.
> Why would this process halt when it works fine if I do not use
> multithreading? Is there a better way of connecting directly to a domain
> controller that would get around this problem?
>
> Thanks,
> Michael.
>
>

1 May 2006 11:37 PM

Michael

Thanks David.

So I can only assume that the declaration that I am using, is using an
instance member which is causing me thread problems. Is there any way around
this because this leads me to believe that you cannot program with the
DirectorySearcher object in a multithreaded application.

Show quoteHide quote

"David Lee Conley" wrote:

> According to the DirectorySearcher class information in the help files:
>
> Any public static (Shared in Visual Basic) members of this type are thread
> safe. Any instance members are not guaranteed to be thread safe.
>
> HTH
>
> Dave
>
> "Michael" <Mich***@discussions.microsoft.com> wrote in message
> news:9B4936F5-BEA0-48D4-B086-9415BB001735@microsoft.com...
> > Hi,
> >
> > I am trying to create a multithreaded VB 2005 application which attempts
> > to
> > create a new thread per Domain Controller (DC) in my environment. Each
> > thread
> > connects to its allocated DC and enumerates all computer objects and
> > extracts
> > the 'LastLogon' property. The results from each thread is then
> > consolidated
> > so that I can get the true lastlogon date for each computer object.
> >
> > However in my routine thats get actioned per thread, I have used the
> > following line which seems to halt each thread and doesn't progress to the
> > next line of code:
> >
> >
> > Dim searcher As New DirectorySearcher("LDAP://" + dc.Domain.ToString & "/"
> > &
> > dc.Name)
> >
> > Where dc is defined as ActiveDirectory.DomainController.
> >
> > This is my method of connecting directly to a specific domain controller.
> > Why would this process halt when it works fine if I do not use
> > multithreading? Is there a better way of connecting directly to a domain
> > controller that would get around this problem?
> >
> > Thanks,
> > Michael.
> >
> >
>
>
>

1 May 2006 6:59 PM

Chris Chilvers

On Sun, 30 Apr 2006 23:52:01 -0700, Michael
<Mich***@discussions.microsoft.com> wrote:

Show quoteHide quote

>Hi,
>
>I am trying to create a multithreaded VB 2005 application which attempts to
>create a new thread per Domain Controller (DC) in my environment. Each thread
>connects to its allocated DC and enumerates all computer objects and extracts
>the 'LastLogon' property. The results from each thread is then consolidated
>so that I can get the true lastlogon date for each computer object.
>
>However in my routine thats get actioned per thread, I have used the
>following line which seems to halt each thread and doesn't progress to the
>next line of code:
>
>
>Dim searcher As New DirectorySearcher("LDAP://" + dc.Domain.ToString & "/" &
>dc.Name)
>
>Where dc is defined as ActiveDirectory.DomainController.
>
>This is my method of connecting directly to a specific domain controller.
>Why would this process halt when it works fine if I do not use
>multithreading? Is there a better way of connecting directly to a domain
>controller that would get around this problem?
>
>Thanks,
>Michael.
>

Could this method call be failing whilst multithreading and generating
an exception? As once moved to another thread this can cause the thread
to silently die.

2 May 2006 12:04 AM

Michael

This is my first real venture into multithreading. I have tried placing
Try...Catch blocks around the 'DirectorySearcher' declaration and also placed
debug.print statements either side. No exceptions are being reported and the
post debug.print statement also doesn't get executed.

If each thread is dieing is there a way to report this back to the main
application thread?

Show quoteHide quote

"Chris Chilvers" wrote:

> On Sun, 30 Apr 2006 23:52:01 -0700, Michael
> <Mich***@discussions.microsoft.com> wrote:
>
> >Hi,
> >
> >I am trying to create a multithreaded VB 2005 application which attempts to
> >create a new thread per Domain Controller (DC) in my environment. Each thread
> >connects to its allocated DC and enumerates all computer objects and extracts
> >the 'LastLogon' property. The results from each thread is then consolidated
> >so that I can get the true lastlogon date for each computer object.
> >
> >However in my routine thats get actioned per thread, I have used the
> >following line which seems to halt each thread and doesn't progress to the
> >next line of code:
> >
> >
> >Dim searcher As New DirectorySearcher("LDAP://" + dc.Domain.ToString & "/" &
> >dc.Name)
> >
> >Where dc is defined as ActiveDirectory.DomainController.
> >
> >This is my method of connecting directly to a specific domain controller.
> >Why would this process halt when it works fine if I do not use
> >multithreading? Is there a better way of connecting directly to a domain
> >controller that would get around this problem?
> >
> >Thanks,
> >Michael.
> >
>
> Could this method call be failing whilst multithreading and generating
> an exception? As once moved to another thread this can cause the thread
> to silently die.
>