Question

I’m looking at writing some PowerShell code that can either execute immediately, or produce the commands it would execute as generated scripts.

I’d like to avoid this scenario:

if($Generating){
  write-Output "somecommand.exe"
} 
else{
  somecommand.exe  
}

I got looking at ScriptBlocks, which at first looked promising because I can write the contents of the ScriptBlock to the console without executing it. Such as:

$sc = { somecommand.exe }
$sc
 somecommand.exe

My specific question is, if my scriptblock contains parameters, can I get them to resolve when I’m writing the scriptblock contents to the console, but WITHOUT invoking the scriptblock?

For example given the following scriptblock:

$b2 = { Param([string]$P) Write-Host "$P" }

When I just type “$b2” at the console and hit enter I see this:

Param([string]$P) Write-Host "$P"

What I’d like to see is this (if the parameter value is “Foo”):

Param([string]$P) Write-Host "Foo"

I realize this can be done when it’s invoked, either via “&” or using Invoke(), but would there be any way to get the parameters to resolve without invoking to make my script generation a little more elegant without needing a bunch of conditional statements throughout the code?

Answer 1

Using some of the suggestions I think I’ve found the best solution for my needs. Consider the following code

function TestFunc
{
    Param(
        [Parameter(Mandatory=$true)]
        [string]$Folder,

        [Parameter(Mandatory=$true)]
        [string]$Foo
    )    

    $code = @"
Write-Host "This is a folder $Folder"
Write-Host "This is the value of Foo $Foo"
"@

    $block = [Scriptblock]::Create($code)

    Write-Host "Running the block"  -BackgroundColor Green -ForegroundColor Black
    &$block

    Write-Host "Displaying block code" -BackgroundColor Green -ForegroundColor Black
    $block

}

And it’s output:

Running the block
This is a folder c:\some\folder
This is the value of Foo FOOFOO
Displaying block code
Write-Host "This is a folder c:\some\folder"
Write-Host "This is the value of Foo FOOFOO"

By doing it this way, I still get all the benefit of keeping my existing functions and their parameters, parameter validation, CBH etc. I can also easily generate the code that the function would execute or just let it execute. Thanks for all the input, it’s definitely been a good learning experience.