Powershell add-member calculated value - arrays

Question

I'm writing a script that takes unstructured input, reformats it and spits out a CSV.
In one of the members, I want to do an NSLOOKUP of another member to get the DNS entry associated with the IP. However, a number of the entries have an IP of 0.0.0.0 e.g. it's a listening port, there's no client yet connected.
These throw up errors from NSLOOKUP, quite rightly, because there's no DNS entry for it.
So, I amended my code to only do the NSLOOKUP if the IP was not 0.0.0.0, otherwise return an empty string.
But I can't make it work.
The following throws up no errors:
$srcdata -split "`r`n"|foreach {
$obj = New-Object System.Object
$obj|Add-Member -MemberType NoteProperty -Name Connection_ID -Value $_.Split(",")[0]
$obj|Add-Member -MemberType NoteProperty -Name Filename -Value $_.Split(",")[1]
$obj|Add-Member -MemberType NoteProperty -Name MCP_Port -Value $_.Split(",")[2]
$obj|Add-Member -MemberType NoteProperty -Name Client_Port -Value $_.Split(",")[3]
$obj|Add-Member -MemberType NoteProperty -Name Port_State -Value $_.Split(",")[4]
$obj|Add-Member -MemberType NoteProperty -Name Client_IP -Value $_.Split(",")[5]
$obj|Add-Member -MemberType NoteProperty -Name Client_DNS -value {If ($obj.Client_IP -ne "0.0.0.0") {(NSLOOKUP $obj.Client_IP|Select-String Name).Line.ToString().Replace(" ","").Split(":")[1]} else {""}}
$obj|Add-Member -MemberType NoteProperty -Name Protocol_Stack -Value $_.Split(",")[6]
$outfile += $obj
}
But then if I inspect one of the objects in the array I see:
Connection_ID : 1
Filename : CCF_MARC1
MCP_Port : 2001
Client_Port : 0
Port_State : LISTEN
Client_IP : 0.0.0.0
Client_DNS : If ($obj.Client_IP -ne "0.0.0.0") {(NSLOOKUP $obj.Client_IP|Select-String Name).Line.ToString().Replace(" ","").Split(":")[1]} else {""}
Protocol_Stack : LEGACY
If I wrap in parentheses instead of in a scriptblock, so the line setting up the Client_DNS is as follows:
$obj|Add-Member -MemberType NoteProperty -Name Client_DNS -value (If ($obj.Client_IP -ne "0.0.0.0") {(NSLOOKUP $obj.Client_IP|Select-String Name).Line.ToString().Replace(" ","").Split(":")[1]} else {""})
I get:
If : The term 'If' is not recognized as the name of a cmdlet, function, script file, or operable program. Check the spelling of the name, or if a path was included, verify that the path is correct and try again.
At K:\CodeSnippets\PowerShell\NW_CONN_TO_CSV.ps1:21 char:91
+ ... NS -value (If ($obj.Client_IP -ne "0.0.0.0") {(NSLOOKUP $obj.Client_IP|Selec ...
+ ~~
+ CategoryInfo : ObjectNotFound: (If:String) [], CommandNotFoundException
+ FullyQualifiedErrorId : CommandNotFoundException
I'm sure I could get it to work as two separate lines of code, so do the If statement and put the result in a variable, then use that variable as the value in the add-member command, but I'm sure what I'm trying to do is eminently possible, I'm just missing something!
Any ideas?

Answer 1

You're interested in a ScriptProperty rather than a NoteProperty:
$obj |Add-Member -MemberType ScriptProperty -Name Client_DNS -Value {
nslookup $this.Client_IP |Select-String Name
}

Answer 2

You could use a regex to extract the name, something like this:
$outfile = $srcdata -split "[\r\n]" | % {
$v = $_.Split(",")
$re = [regex]::match((NSLOOKUP $v[5]), '(?<=Name:\s+)[^\s]+')
New-Object psobject -Property #{
Client_DNS = #('', $re.value)[$re.success]
Connection_ID = $v[0]
Filename = $v[1]
MCP_Port = $v[2]
Client_Port = $v[3]
Port_State = $v[4]
Client_IP = $v[5]
Protocol_Stack = $v[6]
}
}