In powershell i have a function that return me the Ip after an URL, if i use it an loop i always receive an error, what am i doing wrong ?

Hello, i have a function that return as expected the ip after an URL when i call it on it's own.

but if i call my function from within a foreach loop my code ended into the catch block.

here 's the function ---------------------------------------------------------------
 function GetIpAdresse
{
    Param([String] $aServerName)

    try{
        $ip = [System.Net.Dns]::GetHostAddresses($aServerName)

        $ipFinal = $ip[0].IPAddressToString

        return $ipFinal
    }
    catch{
        [system.exception]
        write-host "ko pour url -> ip" + $_
    }
    finally
    {}
}

---------------------------------------------------------------
when i call it from

......
foreach($theServerName in $allServers.Values)
{
      $tempIP = GetIpAdresse $theServerName.ToString()
}
.......


how can i deal with this, i can not find a solution.

thank you in advance for your help

toshi_