Why does the exception not get me in the catch block?

Question

I'm trying to interrogate some service information. Sometimes the installer of the application fails to correctly install, so the registry does not contain a service entry. I want to find out which installer steps did get executed correctly, even on systems that do not have proper logging in the installer.

If MyService does not exist, the script below does not go to the catch block even though the exception handling documentation suggests a bare catch should be enough:

try {
    $path = 'hklm:\SYSTEM\CurrentControlSet\services\MyService'
    $key = Get-Item $path
    $namevalues = $key | Select-Object -ExpandProperty Property |
        ForEach-Object {
        [PSCustomObject] @{
            Name = $_;
            Value = $key.GetValue($_)
        }
    }
    $namevalues | Format-Table
}
catch {
    $ProgramFilesX86 = [System.Environment]::GetFolderPath("ProgramFilesX86");
    $ProgramFiles = [System.Environment]::GetFolderPath("ProgramFiles");
    Write-Host $ProgramFilesX86
    Write-Host $ProgramFiles
}

Why is that and how should I force it to end up in the catch?

This is what PowerShell outputs:

Get-Item : Cannot find path 'HKLM:\SYSTEM\CurrentControlSet\services\MyService' because it does not exist.
At C:\Users\Developer\...\GetMyServiceInfo.ps1:17 char:12
+     $key = Get-Item $path
+            ~~~~~~~~~~~~~~
    + CategoryInfo          : ObjectNotFound: (HKLM:\SYSTEM\Cu...vices\MyService:String) [Get-Item], ItemNotFoundException
    + FullyQualifiedErrorId : PathNotFound,Microsoft.PowerShell.Commands.GetItemCommand

Jeroen Wiert Pluimers · Accepted Answer · 2017-10-26 11:01:08Z

6

Force the error to be terminating:

$key = Get-Item $path -ErrorAction Stop

That way it will throw and catch will get it.

Explanation and links to the official Microsoft documentation:

-ErrorAction is a Common Parameter that can be applied to any PowerShell command
The default value for -ErrorAction is Continue which prevented the exception to be thrown in the first place.
You can configure a global -ErrorAction setting using the Preference Variable named $ErrorActionPreference to override this default value.

edited Oct 26, 2017 at 11:01

Jeroen Wiert Pluimers

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answered Oct 26, 2017 at 8:56

4c74356b41

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2 Comments

Jeroen Wiert Pluimers Over a year ago

Thanks, +1. Please add some links to -ErrorAction and $ErrorActionPreference documentation. Then I will also accept the answer.

Manu Over a year ago

about_CommonParameters

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