Get key name in one member hashtable - powershell

Question

I have a data structure for a multi-level lookup table that looks something like this
$lookupTable = #{
'a' = #{
'a1' = 'A One'
'a2' = 'A Two'
'a3' = 'A Three'
}
'b' = #{
'b1' = 'B One'
'b2' = 'B Two'
'b3' = 'B Three'
}
}
I use a data structure like this to pass an arbitrary number of new and revised values to update the table, like this.
$hash=#{'a'=#{'a4'='A Four'}
'b'=#{'b4'='B Four'}
'c'=#{'c1'='C One'
'c2'='C Two'
}
}
I can then use nested foreach loops to get the key names to add or update.
However, I also need to extract just a single value, and I want to keep a similar data structure so I can pass just one hash table to specify exactly what value I am looking for, such as $getValue = #{'b'='b1'}.
But to do that I need to get the key name at the first(only) index. I have tried
Write-Host "$($getValue.GetEnumerator[0])"
Write-Host "$($getValue.keys.GetEnumerator[0])"
Write-Host "$($getValue.GetEnumerator[1])"
Write-Host "$($getValue.keys.GetEnumerator[1])"
and none work. I could use a foreach again, which will only look once, but that seems inelegant. So, what am I doing wrong?
EDIT: Just to verify the loop based approach works, I did this
foreach ($key in $getValue.keys) {
if ($key) {
Write-Host "$key $($getValue.$key) = $($lookupTable.$key.($getValue.$key))"
}
break
}
and it does indeed come back with b b1 = B one. but what an ugly way to do it.
Dang, getting closer!
$key = $getValue.keys[0] does provide a key of b. But $value = $getValue.$key doesn't return b1 as expected. However, $value = $getValue[$key] does! however, then trying
$key = $getValue.keys[0]
$value = $getValue[$key]
Write-Host "$key $($getValue[$key]) = $($lookupTable.$key.$value)"
doesn't come back with the actual final value. Grr. More coffee and try again.
AHA! $getValue.keys[0] doesn't return a string. But if you cast to a string then everything is dandy. So
$key = [string]$getValue.keys[0]
$value = $getValue.$key
Write-Host "$key $value = $($lookupTable.$key.$value)"
works a treat. So I answered my own question. I guess I'll let the mods decide if this might be educational for others, or should just be deleted.

Answer 1

I think you can simplify this by declaring the $getValue not as a Hashtable, but rather as a simple array:
# define the value to get as array of keys.
# Element 0 => the key for $lookupTable,
# Element 1 => the key for the first nested hash
$getValue = 'b','b1'
# now, simply get the value you are looking for like this:
Write-Host $lookupTable[$getvalue[0]][$getValue[1]]
# or like so:
Write-Host $lookupTable.$($getvalue[0]).$($getvalue[1])
# or by using helper variables:
$lookupKey, $nestedKey = $getValue
Write-Host $lookupTable.$lookupKey.$nestedKey
All of the above will return the value B One