A powershell function to convert a string input of numbers into an array. Handles CSV or ranges.

Convert-StringNumbers.ps1

<#
.Synopsis
   Extracts integers from strings, including CSV and ranges.
.DESCRIPTION
   A longer description that describes what is being done.
   
   
   ####
   # Author: Brent Wright
   # Date Created: 09/16/2019
   # Date Updated: mm/dd/yyyy
   
.EXAMPLE
   Get-StringNumbers 1234

   # Returns: 1234
.EXAMPLE
   "123, 456" | Get-StringNumbers

   # Returns: @(123, 456)
.EXAMPLE
   "10-12" | Get-StringNumbers

   # Returns: @(10, 11, 12)
.NOTES
   Updates:
     mm/dd/yyyy - user.name - fixed a bug, added a new feature...
.COMPONENT
   The component this cmdlet belongs to
.ROLE
   The role this cmdlet belongs to
.FUNCTIONALITY
   The functionality that best describes this cmdlet
#>



function Convert-StringNumbers {
    param([parameter(mandatory = $true, ValueFromPipelineByPropertyName)]
        [ValidateScript({
            if ($_ -match "^(?:\d+)((?:,\s?\d+|-\d+)+)?$") { $true } else {
                throw "[$_] is not valid. Valid formats are: [1234], [1234, 1235, ...], [1234-1240]" }
            })]
        [string]
        $InputObject)
    
    process { 

        $numbers = ($InputObject -split ",").Trim()

        "Num count: {0} - {1}" -f $numbers.count, $($numbers -join ", ") | Write-Verbose

        foreach ($number in $numbers) {

            if ($number -like "*-*") {
                $first, $last = $number -split "-"
                "Range detected..." | Write-Verbose
                ($first..$last)
            } else {
                $number
            }
        }
    }
}