Trapping exceptions

Hi,

I'm just getting into PowerShell and I'm trying to create a simple script
which goes onto the web and drags back some content that it processes further.

What I'm stuggling to do is cope with the exceptions.

I have some code:

$baseUrl = 'http://www.epguides.com/';
$contents = (new-object System.Net.WebClient).DownloadString( $baseUrl +
$title );
$return = [string] '';

trap [System.Net.WebException]
{
$return = "Could not find programme " + $title;
return $return;
}

But any time run with an illegal title (so it 404's), I get error output -
despite wanting to cope with it above in a simple message.

Exception calling "DownloadString" with "1" argument(s): "The remote server
returned an error: (404) Not Found."
At C:\bin\Get-EpisodeList.ps1:4 char:61
+ $contents = (new-object System.Net.WebClient).DownloadString( <<<<
$baseUrl + $title );
Could not find programme 25

What is the correct way of suppressing this?

Additionally, if I ever make this work as a filter, how should I terminate
it then?


Regards,

Ray

You should trap MethodInvocationException, WebException is the inner exception.

PS> $error[0].exception
Exception calling "DownloadString" with "1" argument(s): "The remote server
returned an error: (404) Not Found."
PS> $error[0].exception.gettype()

IsPublic IsSerial Name BaseType
-------- -------- ---- --------
True True MethodInvocationException
System.Management.Automation.MethodException
--
PS> $error[0].exception.innerexception.gettype()

IsPublic IsSerial Name BaseType
-------- -------- ---- --------
True True WebException
System.InvalidOperationException
Wei Wu [MSFT]
Windows PowerShell Team
Microsoft Corporation
This posting is provided "AS IS" with no warranties, and confers no rights.



"Ray Hayes" wrote:

> Hi,
>
> I'm just getting into PowerShell and I'm trying to create a simple script
> which goes onto the web and drags back some content that it processes further.
>
> What I'm stuggling to do is cope with the exceptions.
>
> I have some code:
>
> $baseUrl = 'http://www.epguides.com/';
> $contents = (new-object System.Net.WebClient).DownloadString( $baseUrl +
> $title );
> $return = [string] '';
>
> trap [System.Net.WebException]
> {
> $return = "Could not find programme " + $title;
> return $return;
> }
>
> But any time run with an illegal title (so it 404's), I get error output -
> despite wanting to cope with it above in a simple message.
>
> Exception calling "DownloadString" with "1" argument(s): "The remote server
> returned an error: (404) Not Found."
> At C:\bin\Get-EpisodeList.ps1:4 char:61
> + $contents = (new-object System.Net.WebClient).DownloadString( <<<<
> $baseUrl + $title );
> Could not find programme 25
>
> What is the correct way of suppressing this?
>
> Additionally, if I ever make this work as a filter, how should I terminate
> it then?
>
>
> Regards,
>
> Ray

Ok, I'm trapping MethodInvocationException now. But the console still gets
the exception shown, how should I suppress this? I've already delt with it!

Regards,

Ray

"Wei Wu [MSFT]" wrote:

> You should trap MethodInvocationException, WebException is the inner exception.
>
> PS> $error[0].exception
> Exception calling "DownloadString" with "1" argument(s): "The remote server
> returned an error: (404) Not Found."
> PS> $error[0].exception.gettype()
>
> IsPublic IsSerial Name BaseType
> -------- -------- ---- --------
> True True MethodInvocationException
> System.Management.Automation.MethodException
> --
> PS> $error[0].exception.innerexception.gettype()
>
> IsPublic IsSerial Name BaseType
> -------- -------- ---- --------
> True True WebException
> System.InvalidOperationException
> Wei Wu [MSFT]
> Windows PowerShell Team
> Microsoft Corporation
> This posting is provided "AS IS" with no warranties, and confers no rights.
>
>
>
> "Ray Hayes" wrote:
>
> > Hi,
> >
> > I'm just getting into PowerShell and I'm trying to create a simple script
> > which goes onto the web and drags back some content that it processes further.
> >
> > What I'm stuggling to do is cope with the exceptions.
> >
> > I have some code:
> >
> > $baseUrl = 'http://www.epguides.com/';
> > $contents = (new-object System.Net.WebClient).DownloadString( $baseUrl +
> > $title );
> > $return = [string] '';
> >
> > trap [System.Net.WebException]
> > {
> > $return = "Could not find programme " + $title;
> > return $return;
> > }
> >
> > But any time run with an illegal title (so it 404's), I get error output -
> > despite wanting to cope with it above in a simple message.
> >
> > Exception calling "DownloadString" with "1" argument(s): "The remote server
> > returned an error: (404) Not Found."
> > At C:\bin\Get-EpisodeList.ps1:4 char:61
> > + $contents = (new-object System.Net.WebClient).DownloadString( <<<<
> > $baseUrl + $title );
> > Could not find programme 25
> >
> > What is the correct way of suppressing this?
> >
> > Additionally, if I ever make this work as a filter, how should I terminate
> > it then?
> >
> >
> > Regards,
> >
> > Ray

Use "continue" instead of "return" in your trap block if you don't want to
see this exception.
--
Wei Wu [MSFT]
Windows PowerShell Team
Microsoft Corporation
This posting is provided "AS IS" with no warranties, and confers no rights.



"Ray Hayes" wrote:

> Ok, I'm trapping MethodInvocationException now. But the console still gets
> the exception shown, how should I suppress this? I've already delt with it!
>
> Regards,
>
> Ray
>
> "Wei Wu [MSFT]" wrote:
>
> > You should trap MethodInvocationException, WebException is the inner exception.
> >
> > PS> $error[0].exception
> > Exception calling "DownloadString" with "1" argument(s): "The remote server
> > returned an error: (404) Not Found."
> > PS> $error[0].exception.gettype()
> >
> > IsPublic IsSerial Name BaseType
> > -------- -------- ---- --------
> > True True MethodInvocationException
> > System.Management.Automation.MethodException
> > --
> > PS> $error[0].exception.innerexception.gettype()
> >
> > IsPublic IsSerial Name BaseType
> > -------- -------- ---- --------
> > True True WebException
> > System.InvalidOperationException
> > Wei Wu [MSFT]
> > Windows PowerShell Team
> > Microsoft Corporation
> > This posting is provided "AS IS" with no warranties, and confers no rights.
> >
> >
> >
> > "Ray Hayes" wrote:
> >
> > > Hi,
> > >
> > > I'm just getting into PowerShell and I'm trying to create a simple script
> > > which goes onto the web and drags back some content that it processes further.
> > >
> > > What I'm stuggling to do is cope with the exceptions.
> > >
> > > I have some code:
> > >
> > > $baseUrl = 'http://www.epguides.com/';
> > > $contents = (new-object System.Net.WebClient).DownloadString( $baseUrl +
> > > $title );
> > > $return = [string] '';
> > >
> > > trap [System.Net.WebException]
> > > {
> > > $return = "Could not find programme " + $title;
> > > return $return;
> > > }
> > >
> > > But any time run with an illegal title (so it 404's), I get error output -
> > > despite wanting to cope with it above in a simple message.
> > >
> > > Exception calling "DownloadString" with "1" argument(s): "The remote server
> > > returned an error: (404) Not Found."
> > > At C:\bin\Get-EpisodeList.ps1:4 char:61
> > > + $contents = (new-object System.Net.WebClient).DownloadString( <<<<
> > > $baseUrl + $title );
> > > Could not find programme 25
> > >
> > > What is the correct way of suppressing this?
> > >
> > > Additionally, if I ever make this work as a filter, how should I terminate
> > > it then?
> > >
> > >
> > > Regards,
> > >
> > > Ray