How to create real objects with behavior (methods) in PowerShell?

Probably this question has been answered before.... but I have not found a specific answer to my needs.

BTW I'm using PowerShell 3

Well, I'm new in PowerShell but I have a lot of experience as a C# developer, so working with objects is very important to me.

So I'm wondering if there's a clean way to apply OOP concepts (well not all of them, though that would be awesome) in a PowerShell script, for example there are specific things that I would like to do.

Note: I'm aware that I can write C# code in PowerShell to create DTO's and also that I can create PowerShell binary modules in C#, I have done that in the past, but what I'm looking for now is the ability to write all my code in PowerShell but in an Object Oriented way.

Things I would like to do:

• Create an object in PowerShell, and expose a function written in PowerShell as well, something like this:

  function New-Person
  (
      [Parameter()][string]$firstName
  )
  {
      function Walk()
      {
          Write-Host "Walking...";
      }
  
      $person = New-Object psobject;
  
      $person | Add-Member -MemberType NoteProperty -Name FirstName -Value $firstName;
  
      #This line does not work
      #$person | Add-Member -MemberType CodeMethod -Name Walk -Value Walk;
  
      return $person;
  }
  
  $MyPerson = New-Person -firstName "JP";
  
  $MyPerson;
  
  #This line does not work
  $MyPerson.Walk();
  

• Encapsulate behavior, which means create functions inside my object and then mark them as private

• [Nice to have]. Create base classes so I can inherit and specialize my behavior overriding methods

• [Nice to have]. Create interfaces so I can start thinking in unit testing in isolation my PowerShell methods (I know there are tools like Pester to do this I'm just focusing on OOP features)

What I have done so far is creating objects w