How do I properly pass arguments to a scriptblock using powershell runspaces? - powershell

Question

While using runspaces I would like to pass predictable arguments to my scriptblock from outside. In order to do this without utilizing $args (to avoid making the code less readable), I am storing my argument in a variable called $var and adding the variable to the InitialSessionState of the RunspacePool. To do this I am using the Add method of System.Management.Automation.Runspaces.InitialSessionState.Create().Variables
This works for my purposes, but I also noticed the PowerShell.AddParameter method of [PowerShell]::Create()which would add my parameter to each powershell process as it is created.
And finally there is the PowerShell.AddArgument which I could use like AddParameter, and use a param() block. this would work, however, each argument will be passed in order, and ends up working as well as $args.
So my question is what is the recommended way of passing arguments\parameters\variables into a scriptblock for the purposes I have defined? Is there a performance advantage of one over the other? Can you expand on what purpose you may use one over the other?

Answer 1

You can use cmdlet binding inside of the script block definition.
$ScriptBlock = {
Param (
[int]$NumberofHours,
[string]$ClientName
)
$LogPath = 'd:\Program Files\Exchange\Logging\RPC Client Access\*.LOG'
$today = (Get-Date).AddHours($NumberofHours)
}
Then define call these parameters when you execute the script block.
Invoke-Command -ComputerName $servers -ScriptBlock $ScriptBlock -ArgumentList -1,$cn -ErrorAction SilentlyContinue

Answer 2

Here's my $.02. I know this thread is old but I came across it unanswered while searching for something else.
This example uses a runspace pool to demonstrate how to pass parameters to the script block while using a runspace. The function this comes from passes a datatable to a script block for processing. Some variable names were changed to help with out-of-context readability.
$maxThreads = 5
$jobs = New-Object System.Collections.ArrayList
$rsp = [runspacefactory]::CreateRunspacePool(1,$maxThreads)
$rsp.open()
$params = New-Object 'System.Collections.Generic.Dictionary[string, string]'
$params.Add('Data', $myDataTable)
$params.Add('TableName', $myTableName)
$PS = [powershell]::Create()
$PS.Runspacepool = $rsp
$PS.AddScript($myScriptBlockCode)AddParameters($parameters)
Another option would be to forgo the iDictionary step and simply call .AddParameter repeatedly.
$PS.AddScript($myScriptBlockCode).AddParame'ter(Data',$myDataTable).AddParameter('tableName',$myTableName)
A third way is to pass the parameters as arguments in the order they are defined in your script block
$PS.AddScrip(t$myScriptBlockCode).AddArgument($myDataTable).AddArgument($myTableName)
I hope this helps someone out. I welcome comments as to ways to do this better. As long as the comment doesn't suggest turning it into some amateurish one-liner that no one can read....