Public/Get-ADSIGroupMember.ps1

function Get-ADSIGroupMember
{
<#
.SYNOPSIS
    Function to retrieve the members from a specific group in Active Directory
 
.DESCRIPTION
    Function to retrieve the members from a specific group in Active Directory
 
.PARAMETER Identity
    Specifies the Identity of the Group
     
    You can provide one of the following properties
    DistinguishedName
    Guid
    Name
    SamAccountName
    Sid
    UserPrincipalName
     
    Those properties come from the following enumeration:
    System.DirectoryServices.AccountManagement.IdentityType
 
.PARAMETER Credential
    Specifies alternative credential
 
.PARAMETER Recursive
    Retrieves all the recursive members (Members of group(s)'s members)
     
.PARAMETER DomainName
    Specifies the alternative Domain where the user should be created
    By default it will use the current domain.
     
.PARAMETER GroupsOnly
    Specifies that you only want to retrieve the members of type Group only.
 
.EXAMPLE
    Get-ADSIGroupMember -Identity 'Finance'
     
    Retrieve the direct members of the group 'Finance'
 
.EXAMPLE
    Get-ADSIGroupMember -Identity 'Finance' -Recursive
     
    Retrieve the direct and nested members of the group 'Finance'
 
.EXAMPLE
    Get-ADSIGroupMember -Identity 'Finance' -GroupsOnly
     
    Retrieve the direct groups members of the group 'Finance'
     
.EXAMPLE
    Get-ADSIGroupMember -Identity 'Finance' -Credential (Get-Credential)
     
    Retrieve the direct members of the group 'Finance' using alternative Credential
 
.EXAMPLE
    Get-ADSIGroupMember -Identity 'Finance' -Credential (Get-Credential) -DomainName FX.LAB
     
    Retrieve the direct members of the group 'Finance' using alternative Credential in the domain FX.LAB
     
.EXAMPLE
    $Comp = Get-ADSIGroupMember -Identity 'SERVER01'
    $Comp.GetUnderlyingObject()| select-object *
 
    Help you find all the extra properties
 
.LINK
    https://msdn.microsoft.com/en-us/library/system.directoryservices.accountmanagement.groupprincipal%28v=vs.110%29.aspx?f=255&MSPPError=-2147217396
     
.NOTES
    Francois-Xavier Cat
    lazywinadmin.com
    @lazywinadm
    github.com/lazywinadmin
#>

    [CmdletBinding(DefaultParameterSetName='All')]
    param ([Parameter(Mandatory=$true)]
        [System.String]$Identity,
        
        [Alias("RunAs")]
        [System.Management.Automation.PSCredential]
        [System.Management.Automation.Credential()]
        $Credential = [System.Management.Automation.PSCredential]::Empty,
        
        [System.String]$DomainName,
        
        [Parameter(ParameterSetName='All')]
        [Switch]$Recurse,
        
        [Parameter(ParameterSetName = 'Groups')]
        [Switch]$GroupsOnly
    )
    BEGIN
    {
        Add-Type -AssemblyName System.DirectoryServices.AccountManagement
        
        # Create Context splatting
        $ContextSplatting = @{ ContextType = "Domain" }
        
        IF ($PSBoundParameters['Credential']) { $ContextSplatting.Credential = $Credential }
        IF ($PSBoundParameters['DomainName']) { $ContextSplatting.DomainName = $DomainName }
        
        $Context = New-ADSIPrincipalContext @ContextSplatting
    }
    PROCESS
    {
        TRY
        {
            
            IF ($PSBoundParameters['GroupsOnly'])
            {
                Write-Verbose -Message "GROUP: $($Identity.toUpper()) - Retrieving Groups only"
                $Account = ([System.DirectoryServices.AccountManagement.GroupPrincipal]::FindByIdentity($Context, $Identity))
                $Account.GetGroups()
            }
            ELSE
            {
                Write-Verbose -Message "GROUP: $($Identity.toUpper()) - Retrieving All members"
                IF ($PSBoundParameters['Recursive']) { Write-Verbose -Message "GROUP: $($Identity.toUpper()) - Recursive parameter Specified" }
                # Returns a collection of the principal objects that is contained in the group.
                # When the $recurse flag is set to true, this method searches the current group recursively and returns all nested group members.
                ([System.DirectoryServices.AccountManagement.GroupPrincipal]::FindByIdentity($Context, $Identity)).GetMembers($Recurse)
            }
        }
        CATCH
        {
            $Error[0]
        }
    }
}