How to determine valid variable

i have little function provide common ad info using dsquery:

        function getcontact

        {

            # contacts in domain

            $contact = dsquery contact | cleanadstring | sort

 

            # contacts

            if($contacts.count -eq 0)

            {

                write-host "no contacts found"

            }

            else

            {

                write-host "listing contacts in domain: `n"

                $contacts

                write-host ""

            }

        }

when run function, there may no contacts.  when happens $contacts.count property not valid.  i tried using .gettype() call against variable, but, seems when no hits returned, $contacts variable not longer useful.  how else test see if $contacts variable (for $contacts.length) test valid begin with?

one way change this:

if($contacts.count -eq 0)

to

if(-not $contacts)

if $contacts empty (null) test $false.  if returns anything, test $true.

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