Powershell Group Array of Hashes with Duplicates

Question

I have the following dataset [Array of Hashes]:

---

$dataset = @(
    @{
        ID   = "1234567891"
        Code = "ABC1111"
    },
    @{
        ID   = "1234567892"
        Code = "ABC1111"
    },
    @{
        ID   = "1234567893"
        Code = "ABC1112"  
    },
    @{
        ID   = "1234567894"
        Code = "ABC1113"   
    },
    @{
        ID   = "1234567895"
        Code = "ABC1114"   
    },
    @{
        ID   = "1234567896"
        Code = "ABC1111"  
    }
)

What I am trying to do is to group the following dataset by Code key.

I already tried multiple methods such as piping Group-By , Group-Object , Sort-Object but I'm still not getting the result I want.

What result I am looking to return is a hashtable which looks like so [Or anything similar]:

$groupedDataset = @{
    ABC1111 = @("1234567891","1234567892","1234567896")
    ABC1112 = @("1234567893")
    ABC1113 = @("1234567894")
    ABC1114 = @("1234567895")
}

Answer 1

Convert the hash tables to a PSCustomObjects, group it, then assign it to the new hash table:

$groupedDataset = @{}

$dataset |
    ForEach-Object { [PSCustomObject]$_ } |
    Group-Object -Property Code |
    ForEach-Object { $groupedDataset[$_.Name] = $_.Group.ID }

See Get-Help about_Object_Creation for more information about using [PSCustomObject] to create custom objects from hash tables.

Answer 2

To complement Bacon Bits' helpful answer :

There is no strict need to provide custom objects as input to Group-Object ; [hashtable] instances can be used as-is, as long as you use a script-block argument to access the entry to group by (PSv3+ syntax):

$ht = @{}
$dataset | Group-Object { $_.Code } | ForEach-Object { $ht[$_.Name] = $_.Group.Id }

Note the use of { $_.Code } in lieu of [-Property] Code ; the latter only works with bona fide properties (as opposed to hashtable entries; conversely, however, { $_.Code } works in either scenario, though Code , if applicable, is faster).