Script runs in ISE but not in Powershell - powershell

Question

I have a powershell script. This script runs perfectly fine if I open it in Powershell ISE, however, if I right click on the file and click 'run with powershell' the script throws an error.
Furthermore, I read in previous threads that the following execution pattern solved the issue for some people:
powershell -STA -File script.ps1
In this case this didn't solve the issue, however it did allow me to read the error:
At C:\Users\sancarn\AppData\Local\Temp\script.ps1:20 char:20
+ $parent = [System.Windows.Forms.TreeNode]$global:database.Ite ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Unable to find type [System.Windows.Forms.TreeNode].
At C:\Users\sancarn\AppData\Local\Temp\script.ps1:27 char:36
+ ... [void]$node.nodes.add([System.Windows.Forms.TreeNode]::new(" ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Unable to find type [System.Windows.Forms.TreeNode].
At C:\Users\sancarn\AppData\Local\Temp\script.ps1:33 char:45
+ ... PSCustomObject]IWDBGetChildren([System.Windows.Forms.TreeNode]$node) ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Unable to find type [System.Windows.Forms.TreeNode].
+ CategoryInfo : ParserError: (:) [], ParentContainsErrorRecordException
+ FullyQualifiedErrorId : TypeNotFound
This having been said, I'm not sure I can really do anything about this error specifically... I already load System.Windows.Forms and System.Drawing... Does anyone have any idea how to execute this file properly?
Edit
Other attempts at trying to fix the issue:
powershell -NoExit -STA -File script.ps1
powershell -NoExit -STA -File script.ps1 -Scope Global
Edit 2
I have also tried adding:
Add-Type -AssemblyName System.Windows.Forms
To the top of the powershell script. The issue remains unresolved however.
Edit:
Not sure why this is being flagged as a duplicate after
this answer already has a recommended answer and
the recommended answer demonstrates why this is different.
...

Answer 1

As #PetSerAl said in his comment, the answer is in https://stackoverflow.com/a/34637458
Every PowerShell script is completely parsed before the first statement in the script is executed. An unresolvable type name token inside a class definition is considered a parse error. To solve your problem, you have to load your types before the class definition is parsed, so the class definition has to be in a separate file.
Ultimately to resolve the issue I need to either load my class definitions as a separate file, or store my declarations in a header file, which calls the class definitions (and the rest of the script).
I am amazed this was even an issue but it works now, so that's good...
Edit
In my case it is a bit different to the post linked by the solution author. I'm actually building a ruby library for executing Powershell on windows machines. Currently I don't write data to a file and I can't guarantee that a here-string/invoke-expression will work.
Invoke-Expression #"
$anotherString=#"
hello world!
"#
"# <--- Powershell will throw an error here!
Instead I've decided to encode the body if a header is present, and then decode and execute at runtime
require 'base64'
if header!=""
encoded_body = Base64.strict_encode64(body.encode("utf-16le"))
body = <<-END_TRANSFORMATION
#{header}
$encoded_body = "#{encoded_body}"
Invoke-Expression $([System.Text.Encoding]::Unicode.GetString([System.Convert]::FromBase64String($encoded_body)))
END_TRANSFORMATION
end
So far this has appeared to work in all cases, doesn't need external files, and will work even if users use here-doc strings in their Powershell scripts!