PowerShell: Sort Hash Table Into Ordered Dictionary

PowerShell, Pure Programming

Hello!

PowerShell’s Hash Tables are unordered. The keys don’t always come back in the same order you entered them:

PS /Users/adam/Local/fiddle> $HashTable = @{                   
>>     'a' = 1
>>     'b' = 2
>>     'c' = 3
>>     'd' = 4
>> }
PS /Users/adam/Local/fiddle> $HashTable

Name                           Value
----                           -----
c                              3
b                              2
d                              4
a                              1

I created the hash in the order a, b, c, d but I got back c, b, d, a. That’s normal.

PowerShell also has Ordered Dictionaries that work like Hash Tables but preserve order:

PS /Users/adam/Local/fiddle> $OrderedDictionary = [ordered]@{
>>     'a' = 1
>>     'b' = 2
>>     'c' = 3
>>     'd' = 4
>> }
PS /Users/adam/Local/fiddle> $OrderedDictionary

Name                           Value
----                           -----
a                              1
b                              2
c                              3
d                              4

Today I had large hash and I needed to convert it to a dictionary that was sorted by key name. The hash was returned by a library I didn’t control so I couldn’t just re-define it as a dictionary. I had to convert it. There are a couple ways, but I found this was the cleanest:

$HashTable = @{
    'd' = 4
    'a' = 1
    'b' = 2
    'c' = 3
}
$OrderedDictionary = [ordered]@{}
foreach ($Item in ($HashTable.GetEnumerator() | Sort-Object -Property Key)) {
    $OrderedDictionary[$Item.Key] = $Item.Value
}
$OrderedDictionary

This outputs a dictionary that has been sorted by its keys:

PS /Users/adam/Local/fiddle> ./Ordering.ps1

Name                           Value
----                           -----
a                              1
b                              2
c                              3
d                              4

Because it’s a dictionary and not a regular hash, it’ll keep that ordering.

Happy scripting!

Adam

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