Why Is this Property not being updated when I pass it by reference in PowerShell

Question

Could somebody please explain why the update to the property is not being persisted after the function exits in the example below

function CreateConfigObject
{
    # base solution directory
    $Config = New-Object -typename PSObject

    # Build Config File Contents
    $Config | Add-Member -Name MyProperty -MemberType NoteProperty -Value "Original Value"

    return $Config
}

function MyFunction([ref]$obj)
{
    Write-Host "Inside function Before Updating : " $obj.Value
    Write-host "Are the objects equal? " $obj.Value.Equals($config.MyProperty)

    $obj.Value = "New Value"
    Write-Host "Inside function After Updating : " $obj.Value

}



$config = CreateConfigObject

Write-Host "Before calling function : " $config.MyProperty

MyFunction ([ref]$config.MyProperty)

Write-Host "After calling function : " $config.MyProperty

Answer 1

Took a bit of figuring, but I've got an answer. [ref] passes an object, not a value, to a function. So what you would need to do is pass $config to the function, and then reference it's value, and the .MyProperty property of that value. Look at this slightly altered code to see my point:

function CreateConfigObject
{
    # base solution directory
    $Config = New-Object -typename PSObject

    # Build Config File Contents
    $Config | Add-Member -Name MyProperty -MemberType NoteProperty -Value "Original Value"

    return $Config
}

function MyFunction([ref]$obj)
{
    Write-Host "Inside function Before Updating : " $obj.value.MyProperty
    Write-host "Are the objects equal? " $obj.value.MyProperty.Equals($config.MyProperty)

    $obj.value.MyProperty = "New Value"
    Write-Host "Inside function After Updating : " $obj.value.MyProperty

}



$config = CreateConfigObject

Write-Host "Before calling function : " $config.MyProperty

MyFunction ([ref]$config)

Write-Host "After calling function : " $config.MyProperty

That will output the expected results:

Before calling function :  Original Value
Inside function Before Updating :  Original Value
Are the objects equal?  True
Inside function After Updating :  New Value
After calling function :  New Value