PowerShell catching typed exceptions

Question

I'm having an issue with PowerShell where it will not catch an exception even when the exception is explicitly mentioned in the catch command.

In this case, I'm trying to determine if a ProcessID is still running, and if not then it will take some actions.

The sample code block that I am struggling with is:

    try {
      Get-Process -Id 123123 -ErrorAction 'Stop'
    } 
    catch [Microsoft.PowerShell.Commands.ProcessCommandException] {
      "Caught by Exception Type: Process is missing"
    }
    catch {
    if ($_.Exception.getType().FullName -eq "Microsoft.PowerShell.Commands.ProcessCommandException") {
      "Caught by Catch All: Process is missing"
      }
    }

When this code block is executed the output is:

Caught by Catch All: Process is missing

You would expect the first catch condition to trigger as it names the exception being thrown correctly, but it doesn't trigger.

To make things worse, when the second catch command runs (which catches anything) it queries the name of the exception type and checks if it is "Microsoft.PowerShell.Commands.ProcessCommandException" (which it is) and then takes appropriate steps.

I know I can work around this, but I feel I'm missing a fundamental way about how PowerShell handles Exceptions.

Can anyone shed light on this for me?

Shay Levy · Accepted Answer · 2011-12-05 06:37:48Z

28

When you set ErrorAction to Stop, non-terminating errors are wrapped and thrown as type System.Management.Automation.ActionPreferenceStopException, this is the type you want to catch.

try 
{
    Get-Process -Id 123123 -ErrorAction Stop
} 
catch [System.Management.Automation.ActionPreferenceStopException]
{
    ... do something ...
}

answered Dec 5, 2011 at 6:37

Shay Levy

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8 Comments

David Thomas Over a year ago

Thank you very much, that was it. I was sure it was being wrapped in something but for the life of me I couldn't workout what the wrapping exception type was. At least once caught that way I can query on the .getType().FullName to validate the error type. Interestingly, it doesn't matter if -ErrorAction 'Stop' is used or $ErrorActionPreference = 'Stop' the result is the same.

Shay Levy Over a year ago

Yes, and I prefer to change it on the cmdlet level so I don't need to revert the global value each time I change its value..

user337598 Over a year ago

Hi, is there a explanation of how we get from the generalized object type 'Microsoft.PowerShell.Commands.ProcessCommandException' to 'System.Management.Automation.ActionPreferenceStopException' ? I'm trying to catch a exception for another class or error and get stuck in the same place as @david-thomas did.

Justin Helgerson Over a year ago

@ShayLevy If you would like your script to stop execution when an error occurs is there any way to catch typed exceptions? We often set the ErrorActionPreference variable to have our scripts stop executing. How could I inspect the type of exception in that case?

TurtleZero Over a year ago

7 years later: it looks like powershell doesn't wrap these exceptions anymore, and the real exception type can be captured..

|

Benjamin Zach · Accepted Answer · 2021-11-19 01:44:53Z

-1

Maybe cause you are missing an error action

try 
{ 
    kill 1234567 -ErrorAction Stop 
} 
catch 
{ 
    Write-Host "Blam!" 
}

edited Nov 19, 2021 at 1:44

Benjamin Zach

1,6412 gold badges21 silver badges43 bronze badges

answered Nov 17, 2021 at 10:40

Grzes

1

1 Comment

Benjamin Zach Over a year ago

Could you please provide a bit more explanation about how your solution solves the issue.

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