I have a script to which I pass server name(s) in $args.

This way I can do stuff to this (these) server(s) using foreach :

.\script.ps1 host1 host2 host3
foreach ($i in $args)
    Do-Stuff $i
I'd like to add a named optional parameter called vlan. I've tried:
Param(
    [string]$vlan
foreach ($i in $args)
    Write-Host $i
Write-Host $vlan
It works if you pass a -vlan parameter but if you don't then the script auto assigns the last server name to $vlan.
So, how can you pass single or multiple parameters plus an optional named parameter to a PowerShell script?
Ideally, here are valid examples:
.\script.ps1 host1
.\script.ps1 host1 host2 host3
.\script.ps1 host1 host2 -vlan office
The easiest way is probably to use two parameters: One for hosts (can be an array), and one for vlan.
param([String[]] $Hosts, [String] $VLAN)
Instead of
foreach ($i in $args)
you can use
foreach ($hostName in $Hosts)
If there is only one host, the foreach loop will iterate only once. To pass multiple hosts to the script, pass it as an array:
myScript.ps1 -Hosts host1,host2,host3 -VLAN 2
...or something similar.
                thanks for including the info on how to call the script - I'm often missing little pieces like that in powershell.
                    – Jan Bühler
                Feb 21 '18 at 16:00
Parameters take input before arguments. What you should do instead is add a parameter that accepts an array, and make it the first position parameter. ex:
param(
    [Parameter(Position = 0)]
    [string[]]$Hosts,
    [string]$VLAN
foreach ($i in $Hosts)  
    Do-Stuff $i
Then call it like:
.\script.ps1 host1, host2, host3 -VLAN 2
Notice the comma between the values. This collects them in an array  
 param(
       [Parameter(Position=0)][String]$Vlan,
       [Parameter(ValueFromRemainingArguments=$true)][String[]]$Hosts
    ) ...
This would allow multiple hosts to be entered with spaces.
                Really nice! Except your example is missing a ']' to close the second Parameter attribute.
                    – Sebastiaan M
                Jun 3 '18 at 4:55
I call a scheduled script who must connect to a list of Server this way:
Powershell.exe -File "YourScriptPath" "Par1,Par2,Par3"
Then inside the script:
param($list_of_servers)
Connect-Viserver $list_of_servers.split(",")
The split operator returns an array of string
        
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