Recursive Group Member

Function Get-RecursiveCloudGroups
{

    [cmdletbinding()]

    param(

        [parameter(Mandatory = $True, ValueFromPipeline = $true)]
        $CloudGroup,

        [Parameter(Mandatory = $False, DontShow = $True)]
        [System.Collections.Generic.HashSet[guid]] $DontCheck
    )

    Begin
    {
        If (-not(Get-AzureADCurrentSessionInfo))
        {
            Connect-AzureAD
        }
        $list = New-Object 'System.Collections.Generic.List[object]'
        if (-not $PSBoundParameters.ContainsKey("DontCheck"))
        {
            $DontCheck = New-Object 'System.Collections.Generic.HashSet[guid]'
        }
    }

    Process
    {
        $members = @(Get-AzureADGroupMember -ObjectId $CloudGroup.ObjectId)

        $groups, $users = $members.Where({$_.ObjectType -eq "Group"}, "Split")

        if ($groups.Count -gt 0)
        {
            foreach ($g in $groups.Where({$DontCheck -notcontains $_.ObjectId}))
            {
                [void]$DontCheck.Add($g.ObjectId)
                $recurseCheck = Get-RecursiveCloudGroups -CloudGroup $g -DontCheck $DontCheck

                $DontCheck.UnionWith($recurseCheck.DontCheck)

                foreach ($mm in $recurseCheck.Members.Where({-not $list.Contains($_)}))
                {
                    $list.Add($mm)
                }
            }
        }
        if ($users.Count -gt 0)
        {
            foreach ($u in $users.Where({-not $list.Contains($_)}))
            {
                $list.Add($u)
            }
        }
    }
    End
    {
        if ($PSBoundParameters.ContainsKey("DontCheck"))
        {
            [pscustomobject]@{
                Members = $list
                DontCheck = $DontCheck
            }
        }
        else
        {
            $list
        }
    }
}