Use Hashtable with switch case in PowerShell - powershell

Question

I would need to make some decisions in PowerShell based on values in a hashtable.
Basically I need to assign users' UPN in Active Directory according to an attribute, the company one, and thought to create a hashtable containing keys and values like this
Key Value
Company1 #Company1.com
Company2 #Company2.com
The issue I am facing is I don't know how to tell PowerShell to use a value rather than another based on the company attribute, basically I don't know how to cycle/check the company attribute against the key in the hashtable.
I've tried to use switches like
$a -match $hashTable
or
$a -contains $hashtable
with little success.
I think a hashtable is what I need here, but I am of course open to any suggestion like using external files for the match as the number of the companies I need to match is rather high.

Answer 1

While Mathias already presented a proper solution I'd like to add some more explanation.
Hashtables and switch statements are essentially two different solutions to the same problem: transform an input value to a corresponding output.
A → "foo"
B → "bar"
C → "baz"
...
Hashtables are the simpler (and faster) approach, where you look up the result to the input value in a pre-defined table. Their advantage is that you can implement the associations in one place (e.g. a declaration section of your code where you define all your (static) data) and use them in a very simple manner anywhere else in your code:
$domains = #{
'Company1' = '#Company1.com'
'Company2' = '#Company2.com'
}
$name = 'foo'
$company = 'Company1'
$addr = $name + $domains[$company]
switch statements are more complicated in their handling, but also a lot more versatile. For instance, they allow different kinds of comparisons (wildcard, regular expression) in addition to simple lookups. They also allow providing default values/actions if a value is not listed. With hashtables you need to handle those cases with an additional if/else statement like Mathias showed, unless you're fine with the empty value that hashtables return when the lookup doesn't find a match.
$name = 'foo'
$company = 'Company1'
$domain = switch ($company) {
'Company1' { '#Company1.com' }
'Company2' { '#Company2.com' }
default { throw 'Unknown company' }
}
$addr = $name + $domain

Answer 2

-match and -contains are not "switches" but operators.
The -match operator takes a string as its left hand side argument and compares it to a regular expression pattern, which your $hashtable is a poor substitute for.
The -contains operator takes a collection (an array or list) as its left hand side argument and compares it to a scalar value on the right, to see if the collection, well contains the scalar value. Also not immediately applicable to your hashtable.
You can use the ContainsKey() method to test whether a given key exists, then use an indexer ($table[$key]) to extract the value:
$UPNSuffix = if($HashTable.ContainsKey($User.Company)){
# Company name exists in hashtable extract UPN suffix
$HashTable[$User.Company]
}
else {
# Not found, return default UPN suffix
"#default.company1.com"
}
Alternatively use the -contains operator on the Keys of the hashtable in place of ContainsKey():
$UPNSuffix = if($HashTable.Keys -contains $User.Company){
# Company name exists in hashtable extract UPN suffix
$HashTable[$User.Company]
}
else {
# Not found, return default UPN suffix
"#default.company1.com"
}