powershell - Test if registry value exists

Question

In my powershell script I'm creating one registry entry for each element I run script on and I would like to store some additional info about each element in registry (if you specify optional parameters once then by default use those params in the future).

The problem I've encountered is that I need to perform Test-RegistryValue (like here--see comment) but it doesn't seem to do the trick (it returns false even if entry exists). I tried to "build on top of it" and only thing I came up is this:

Function Test-RegistryValue($regkey, $name) 
{
    try
    {
        $exists = Get-ItemProperty $regkey $name -ErrorAction SilentlyContinue
        Write-Host "Test-RegistryValue: $exists"
        if (($exists -eq $null) -or ($exists.Length -eq 0))
        {
            return $false
        }
        else
        {
            return $true
        }
    }
    catch
    {
        return $false
    }
}

That unfortunately also doesn't do what I need as it seems it always selects some (first?) value from the registry key.

Anyone has idea how to do this? It just seems too much to write managed code for this...

Answer 1

Personally, I do not like test functions having a chance of spitting out errors, so here is what I would do. This function also doubles as a filter that you can use to filter a list of registry keys to only keep the ones that have a certain key.

Function Test-RegistryValue {
    param(
        [Alias("PSPath")]
        [Parameter(Position = 0, Mandatory = $true, ValueFromPipeline = $true, ValueFromPipelineByPropertyName = $true)]
        [String]$Path
        ,
        [Parameter(Position = 1, Mandatory = $true)]
        [String]$Name
        ,
        [Switch]$PassThru
    ) 

    process {
        if (Test-Path $Path) {
            $Key = Get-Item -LiteralPath $Path
            if ($Key.GetValue($Name, $null) -ne $null) {
                if ($PassThru) {
                    Get-ItemProperty $Path $Name
                } else {
                    $true
                }
            } else {
                $false
            }
        } else {
            $false
        }
    }
}