Powershell and argument issue

I was creating very simple function today, however got stuck there for a while…

As you can see below, function is very, very simple:
Function Global:Security\Encrypt-String ([string]$Input){Return [LoginConsultants.Crypto.Password]::EnCrypt($Input)}

It’s using our library to encrypt some text… To my surprise, it didn’t work however. After a little investigation, it turned out that I made rookie mistake – I used $Input, while it is reserved variable :) Very, very stupid mistake of course, I was just surprised that Posh doesn’t complain if you use such parameter.

Anyway, below is small function you can use to test if parameter you want to use is valid:
function Test-ParameterName ([string]$Name) {
           Return [boolean]$($(Test-Path Variable:$Name) -eq 0)
}

As you can see, it’s extremely primitive, only interesting part is Return [boolean]$($(Test-Path Variable:$Name) -eq 0) – meaning of this function is to revert boolean value. So if Test-Path is $True, function will return $False and if Test-Path is $False, it will return $True. I remember that some years ago I used [boolean]$Foo – 1 in .NET, however it is not supported in Powershell itself (operator – is not defined for [boolean] and [int]).

Martin