PowerShell Switch Statement Issue - powershell

Question

I have the following simple code and it isn't working (simplified from a much larger function)
The user in my first example doesn't exist in my use case
The switch statement doesn't work
A break-point (using ISE) on both the statements in the first switch never get triggered
The second example works without issue
The third code snippet is some troubleshooting code to prove $myADObject is null
What am I missing?
Snippet 1:
$user = "no.one"
$myADUsr = Get-ADObject -Filter { sAMAccountName -like $user }
switch ($myADUsr) {
$null { 'User object variable is null' }
default { 'User object variable has a value' }
}
Snippet 2:
$myADUsr = $null
switch ($myADUsr) {
$null { 'The variable is null' }
default { 'The variable has a value' }
}
Snippet 3:
clear-host
$member = "no.one"
$adobject = Get-ADObject -Filter { sAMAccountName -like $member }
'=== Frist switch ==='
switch ($adobject) {
{$null} { "tests as null"}
{$null -eq $_ } { 'another null test' }
{[string]::IsNullOrEmpty($_)} {'string null test'}
{$_ -eq [string]::Empty} { 'another string null test'}
{$null -ne $_ } { 'not null' }
default { "I don't think this is working ..." }
}
'==== if ====='
If ($null -eq $adobject) { 'null' } else { 'not null' }
'==== second switch ==='
$nullvariable = $null
switch ($nullvariable) {
$adobject { 'null object' }
$null { "null"}
default { "not null" }
}

Answer 1

The switch statement implicitly operates on collections (enumerable data types), and evaluates its branches for each element of the enumeration.
A function or cmdlet call that yields no output technically outputs the [System.Management.Automation.Internal.AutomationNull]::Value singleton, which can be conceived of as an array-valued $null - that is, in enumeration contexts such as switch it behaves like an empty collection: there's nothing to enumerate.
Therefore, because $myADUsr in your example contains [System.Management.Automation.Internal.AutomationNull]::Value due to Get-AdUser not producing any output, the switch statement is effectively skipped.
If all you need to know is whether an AD user object was returned, use PowerShell's implicit to-Boolean conversion in an if statement, because in an expression context [System.Management.Automation.Internal.AutomationNull]::Value behaves like $null (and therefore evaluates to $false):
$myADUsr = Get-ADObject -Filter 'sAMAccountName -like $user'
if ($myAdUsr) {
'User object variable has a value'
}
else {
'User object variable is null'
}

Answer 2

It think updating my original snippet #1 like this gets me out of trouble, it seems to work so I can continue to use the switch statement I have already written. I'm still testing.
$user = "no.one"
$myADUsr = Get-ADObject -Filter "sAMAccountName -like '$user'"
if ( #($myADUsr).Count -eq 0 ) { $myADUsr = $null }
switch ($myADUsr) {
$null { 'User object variable is null' }
default { 'User object variable has a value' }
}