passing powershell variables to C# code within PS script

Question

I read a lot about passing vars from C# to powershell script but i am interesten in the other way around.

here I have this code to create a Type in my powershell script:

Add-Type @'

public class Node
{

    public string Type;
    public string VM_Name;
    public string VM_IP;
    public string Hostname;

}
'@

$vm1 = New-Object Node
$vm2 = New-Object Node
$vm3 = New-Object Node
$vm4 = New-Object Node

After this code I have C# code:

$sourceCode = @'


public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
    }

    private void InitializeComponent()
    {
    }
}

'@

How I might be able to access $vm1,2,3,4 in the C# code above ?

Keith Hill · Accepted Answer · 2014-03-14T20:19:43.477

You could either pass the variables into the type via a method in your C# class that would accept the variables as parameters e.g.:

$form = new-object Form1
$form.SetVariables($vm1, $vm2, $vm3, $vm4)

I recommend that approach.

Another option (heavier weight and not tested) is to try accessing the current runspace from the C# code e.g.:

var defRunspace = System.Management.Automation.Runspaces.Runspace.DefaultRunspace;
var pipeline = defRunspace.CreateNestedPipeline();
pipeline.Commands.AddScript("$vm1,$vm2,$vm3,$vm4");
var results = pipeline.Invoke();
var vm1 = results[0];
var vm2 = results[1];
...

I haven't tried this from C# code (only from within PowerShell) so I'm not 100% sure it will work.

Mark Llewellyn · Answer 2 · 2021-02-05T16:49:12.033

A way to pass variables to C# scripts running inside Powershell is to use an HttpListener (monitoring a localhost port) that harvests the Content-Type. The Content-Type field can take up to 16,000 characters, and I used it to prevent colleagues on your machine using a browser to create spurious input.

The listener shown here is in a stand-alone Powershell script:

Add-Type -TypeDefinition @'

using System;
using System.Threading.Tasks;
using System.Net;
using System.Windows.Forms;

namespace LocalHostListener
{
    public class Program
    {
        HttpListener listener = new HttpListener();

            public static void Main(string[] args)
            {
                    Program program = new Program();
                    program.Start(args[0]);
            }

            public void Start(string url_)
            {
                    listener.Prefixes.Add(url_);
                    listener.Start();
                    listener.BeginGetContext(new AsyncCallback(GetContextCallback), null);
                    Console.ReadLine();
                    listener.Stop();
            }

            public void GetContextCallback(IAsyncResult result)
            {
            HttpListenerContext context = listener.EndGetContext(result);
            HttpListenerRequest request = context.Request;
            HttpListenerResponse response = context.Response;

            Task.Factory.StartNew(() => 
            {
                // KICK OFF YOUR UPDATE ACTIONS HERE (THE LENGTH FILTER EXCLUDES BROWSER CALLS)
                if(request.ContentType.Length>0) yourAction(request.ContentType);
            });

                // SEND A RESPONSE TO KEEP POWERSHELL Invoke-WebRequest,
                // BROWSERS AND VBS MSXML2.XMLHTTP.6.0 HAPPY
                // (C# HttpWebRequest DOESN'T CARE)
                    response.ContentLength64 = 1;
            response.OutputStream.WriteByte(Convert.ToByte('!'));

                    listener.BeginGetContext(new AsyncCallback(GetContextCallback), null);
            }

        public void yourAction(string update)
        {
            Console.WriteLine(update); 
            MessageBox.Show(new Form(), update,"Message from localhost feed",
             MessageBoxButtons.OK,MessageBoxIcon.None,
               MessageBoxDefaultButton.Button1,(MessageBoxOptions)0x40000);
        }
    }
}

'@ -Language CSharp -ReferencedAssemblies System.Windows.Forms

$Host.UI.RawUI.WindowTitle='Monitoring "Content-Type" on http://localhost:1959'
[LocalHostListener.Program]::Main('http://localhost:1959/')

You can then update the listener using the Powershell WebRequest:

Invoke-WebRequest -ContentType 'Your message here' -URI http://localhost:1959

Updates can also be sent to the listener using a C# sender that sets the Content-Type with your variables (again, shown here in a stand-alone Powershell script):

Add-Type -TypeDefinition @'

using System;
using System.Net;

namespace LocalHostSender
{
    public class Program
    {
        public static void Main(string[] args)
        {
            try{
                    HttpWebRequest request = (HttpWebRequest)WebRequest.Create("http://localhost:1959");
                    request.ContentType = args[0];
                    request.Timeout = 200;
                    request.GetResponse();          
            }catch{}
        }
    }
}

'@ -Language CSharp -ReferencedAssemblies System.Net

[LocalHostSender.Program]::Main("Your message here")

The response section of the listener script can be removed if only the C# sender is used.

Another advantage with this method is that VBS scripts can also update the Content-Type:

text_ = "Your message here"

Randomize
Set req = CreateObject("MSXML2.XMLHTTP.6.0")
req.open "GET", "http://localhost:1959/" & rnd, False
req.setRequestHeader "Content-Type", text_
req.send
'req.responseText

The random addition to the page request is required if you want to loop multiple requests, as MSXML2.XMLHTTP.6.0 doesn't send Content-Type information on identical page requests.

If you actually wanted browser/HTML access you could harvest the page requests in the listener using:

string simplePageRequest_ = request.Url;
//Parsing "favicon.ico" and "http://localhost:1959/"

string pageQuery_ = request.QueryString["q"];

updating via the browser page requests, or again using the Powershell WebRequest:

Invoke-WebRequest 'http://localhost:1959/Your message here'
Invoke-WebRequest 'http://localhost:1959/?q=Your message here'

passing powershell variables to C# code within PS script

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