passwordgen.ps1

using namespace System.Collections.Generic

class PasswordGen {
    [int] $Length = 20
    [int] $NonAlphaCount = 7
    [string] $Password

    PasswordGen () {
        $this.GetNewPassword()
    }

    PasswordGen ([int] $Length, [int] $NonAlphaNumCount) {
        $this.GetNewPassword($Length, $NonAlphaNumCount)
    }

    PasswordGen ([int] $Length) {
        $this.GetNewPassword($Length, $this.NonAlphaCount)
    }

    [void] GetNewPassword() {
        $this.GetNewPassword($this.Length, $this.NonAlphaCount)
    }

    [void] GetNewPassword([int] $Length, [int] $NonAlphaNumCount) {
        if($Length -gt [int]::MaxValue / 20) {
            throw [System.ArgumentException]::new(
                'Length is too big!',
                'Length'
            )
        }

        if($Length -lt $NonAlphaNumCount) {
            throw [System.ArgumentException]::new(
                'Length cannot be lower than Non-Alphanumeric char count.',
                'NonAlphaNumCount'
            )
        }

        $this.Length = $Length
        $this.NonAlphaCount = $NonAlphaNumCount

        $CharSet = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890'
        $NonAlphaNum = '!@#$%^&*()_-+=[{]};:<>|./?'
        $ran = [random]::new()
        $passw = [char[]]::new($Length)
        $charLength = $Length - $NonAlphaNumCount

        for($i = 0; $i -lt $charLength; $i++) {
            $passw[$i] = $CharSet[$ran.Next($CharSet.Length)]
        }
        for($i = $i; $i -lt $Length; $i++) {
            $passw[$i] = $NonAlphaNum[$ran.Next($NonAlphaNum.Length)]
        }

        $this.Password = $this.Shuffle([string]::new($passw))
    }

    [void] Shuffle() {
        $this.Password = $this.Shuffle($this.Password)
    }

    [string] Shuffle ([string]$Passw) {
        $ran = [random]::new()
        $shuffled = [char[]]::new($Passw.Length)
        $shuffle = [List[Char]]::new()
        $shuffle.AddRange($Passw.ToCharArray())

        for($i = 0; $i -lt $Passw.Length; $i++) {
            $item = $ran.Next($shuffle.Count)
            $shuffled[$i] = $shuffle[$item]
            $shuffle.RemoveAt($item)
        }

        return [string]::new($shuffled)
    }
}

$p = [PasswordGen]::new()