join quoted strings with variable in powershell

Question

I'm coming from a *nix scripting background and I'm a total newbie to powershell and Windows admin in general. I'm trying to write a script that will check the SmartHost value on a collection of exchange/IIS smtp virtual hosts. I'm trying to figure out how to insert the looped variable into the ADSI query string but the + operator doesn't do the trick:

$hosts = @("host1","host2")

foreach ($hostname in $hosts) {
$SMTPSvc = [ADSI]'IIS://' + $hostname + '/smtpsvc/1'
echo $SMTPSvc.SmartHost
}

Using the + with single or double quotes gives me this error:

Method invocation failed because [System.DirectoryServices.DirectoryEntry] does not contain a method named 'op_Addition'. At line:3 char:1 + $SMTPSvc = [ADSI]'IIS://' + $hostname + '/smtpsvc/1' + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + CategoryInfo : InvalidOperation: (op_Addition:String) [], RuntimeException + FullyQualifiedErrorId : MethodNotFound

What would be the proper or preferred way to insert the looped host value into the ADSI query string?

Answer 1

It looks like an order of operations issue. The first part of the query:

[ADSI]'IIS://'

is being converted to the query string and then you try to add a string to the resulting [System.DirectoryServices.DirectoryEntry] object. Since that class does not provide an addition operator, it fails. Instead, generate the entire string first before constructing the query by enclosing it in brackets:

$SMTPSvc = [ADSI]('IIS://' + $hostname + '/smtpsvc/1')