Split hastable at key/value pair - powershell

Question

How can I split a hashtable starting from a specific key/value pair?
I have hashtable like the following, just longer:
Name Value
---- -----
Name Alpha
Age 2
Position Trick
Start date 01-01-31
End date Unknown
Name Corax
Age 21
Position Sneak
Earnings 40'000
End Date Unknown
Name Horus
Age 22
Position Dead
Why Heresy
End date 03-30-30
I tried Group-Object but it failed.
I particularly wanted to separate it by Name and everything aside from Name, Age and Position are not consistent.
My actual issue is that I want to parse the hashtable for the Name and Age when Why = Heresy, and unfortunately, the original source of the data is a list of strings, which is the reason why I convert it to a hashtable.

Answer 1

Hashtables are not ordered, so you can't rely on a concept of "before" and "after". If you know the specific names of one complete set of keys, then you can loop through the hashtable and build two new ones, so if you wanted one hashtable to contain the Name, Age, and Position, and the other to contain everything else, you can do something like this:
$New1 = #{}
$New2 = #{}
$KeysGroup1 = #('Name','Age','Position') # This could just be one value
$MyHashTable.GetEnumerator().ForEach({
if ($_.Key -in $KeysGroup1) {
$New1[$_.Key] = $_.Value
} else {
$New2[$_.Key] = $_.Value
}
})
You can use an ordered dictionary if order is important for you. You can use a shortcut to create a literal ordered dictionary by preceding a literal hashtable with the [ordered] type accelerator:
$myOrdered = [ordered]#{ a = 1; z = 5; g = 2 }
From there you could do a similar approach to above that relies on order.
To create an ordered dictionary that isn't based on a literal:
$myOrdered = New-Object System.Collections.Specialized.OrderedDictionary
# or in PowerShell v5
$myOrdered = [System.Collections.Specialized.OrderedDictionary]::new()
$myOrdered.Add('key','value')
Edit based on comments
It sounds more like what you have is an array of hashtables and you now want to go about filtering these.
A [hashtable] can (and is often) used as a sort of proto-object, and it can be very useful for that because it often supports the same syntax, and it has built-in literal support.
But you're starting to run into their limits, and at this point I think you want to be dealing with an array of objects and not an array of hashtables.
Luckily, there are really easy ways to create objects in PowerShell right from a hashtable:
$obj = New-Object -TypeName PSObject -Property $myHash
$obj = [PSCustomObject]$myHash
$objArray = $myHashArray.ForEach({[PSCustomObject]$myHash})
Once you've got your array of objects, the real fun begins:
$heretics = $objArray.Where({$_.Why -eq 'Heresy'})
You'll notice I didn't even bother filtering out the other properties here. You shouldn't, until you really need to. Then you can use Select-Object or just access the properties you need. So for display purposes you might just do:
$heretics | Format-Table Name,Age
There's more stuff you can do with an object that you can't with hashtables, like add special types of properties:
$objArray | Add-Member -MemberType ScriptProperty -Name IsHeretic -Value { $this.Why -eq 'Heresy' } -Force
$heretics = $objArray.Where({$_.IsHeretic})

Answer 2

So, in the end; I figured something out, Thanks a lot to #briantist for guidance to the right direction.
My solution code is:
$startobj = (0..($hastable.count -1)) | where {$hashtable[$_].keys -like "*Name*"}
$endobj = (0..($hashtable.count -1)) | where {$hashtable[$_].keys -like "*End date*"}
$objindex = (0..($hashtable.count -1))
$numberofobjindex = 0..($hashtable.Where({$_.keys -like "*Name*"}).count - 1)
$hashtableparsed = foreach ($numba in $numberofobjindex) {
$Conv2data = $hashtable[($startobj[$numba]..$endobj[$numba])]
[PSCustomObject] #{
Name = $Conv2data.Name
Age = $Conv2data.Age
Why = $Conv2data.Why
}
}
$hashtableparsed
I realized that the hashtable data I was presented with had a repeating pattern with Name at the start of each cycle, and End date at the end.
So I basically did an indexing of the hashtable, and marked and indexed all instances where the cycle would start and end.
I then counted the cycles, and FOR EACH cycle captured the data of hashtable data in the lines particularly of that cycle and turned it into a PSCustomObject