New-PSHostSession.ps1

function New-PSHostSession {
    [CmdletBinding(DefaultParameterSetName = 'ById')]
    param (
        [Parameter(ParameterSetName = 'ById', Mandatory = $true, Position = 0)]
        [int] $Id,

        [Parameter(ParameterSetName = 'ByProcess', Mandatory = $true, ValueFromPipeline = $true)]
        [System.Diagnostics.Process] $Process,

        [Parameter(ParameterSetName = 'ByCustomPipeName', Mandatory = $true)]
        [string] $CustomPipeName,

        [Parameter(ParameterSetName = 'AllSets')]
        [string] $AppDomainName,

        [Parameter(ParameterSetName = 'AllSets')]
        [int] $OpenTimeout = 2000
    )

    process {
        if ($PSCmdlet.ParameterSetName -eq 'ById') {
            $ProcessId = $Id
        } elseif ($PSCmdlet.ParameterSetName -eq 'ByProcess') {
            $ProcessId = $Process.Id
        }

        if ($PSCmdlet.ParameterSetName -eq 'ByCustomPipeName') {
            $ConnectionInfo = [System.Management.Automation.Runspaces.NamedPipeConnectionInfo]::new($CustomPipeName)
            $TransportName = $CustomPipeName
        } else {
            $ConnectionInfo = [System.Management.Automation.Runspaces.NamedPipeConnectionInfo]::new($ProcessId)
            $TransportName = "NamedPipe:${ProcessId}"
        }

        $ConnectionInfo.OpenTimeout = $OpenTimeout

        if ($AppDomainName) {
            $ConnectionInfo.AppDomainName = $AppDomainName
        } elseif ($PSCmdlet.ParameterSetName -ne 'ByCustomPipeName') {
            $PSHostProcessInfo = Get-PSHostProcessInfo $ProcessId
            $ConnectionInfo.AppDomainName = $PSHostProcessInfo.AppDomainName
        }

        $TypeTable = [System.Management.Automation.Runspaces.TypeTable]::LoadDefaultTypeFiles()
        $Runspace = [RunspaceFactory]::CreateRunspace($ConnectionInfo, $Host, $TypeTable)
        $Runspace.Open()

        [System.Management.Automation.Runspaces.PSSession]::Create($Runspace, $TransportName, $null)
    }
}