Programmatically create Storyboard / Window

Hi Xamarin,
I'm an experienced WinForms and WPF C# developer. I just got my first mac and I'm busy figuring things out.

There is an app that I've written that is heavily plugin based. The WPF version is completely GUI-less except for a login screen that it presents at the very beginning of the app - and even this login screen is loaded by a plugin.

Anyways, I'm trying to figure out the Cocoa "version" of this code:

var Login = new frmLogin();
Login.ShowDialog();

I specifically don't want there to be a "main" storyboard.

I've created a new Storyboard (named "Storyboard1") and put a new window in it. I have the following classes:
Window Controller: Window1Controller
Window: Window1
Story Board Controller: Storyboard1ViewController

I understand that I need to call StoryBoard.InstantiateControllerWithIdentifier(...) to get the Window1 Controller, but it seems as though whatever string I pass, gives me an error.

What should I pass?

Here's the code I'm using to try to figure out what I should use for the controller name.

using System.Linq;
using System;

namespace Test3 {
static class MainClass {
static void Main(string[] args) {

        NSApplication.Init();


        var StoryBoards = new[] { "Storyboard1", "Storyboard2" };
        var Controllers = new[] {
            "ViewController",
            "Window1Controller", "Window2Controller",
            "Storyboard1ViewController", "Storyboard2ViewController"
        };

        var items =
            from x in StoryBoards
            from y in Controllers
            let Result = LoadController(x, y)
            where Result != null
            select new {
                Storyboard = x,
                Controllers = y,
                Result = Result
            }
        ;

        var Values = items.ToList();

}

    private static object LoadController(string StoryBoard, string Controller) {
        var ret = default(object);
        try {
            var sb = NSStoryboard.FromName(StoryBoard, null);

            var con = sb.InstantiateControllerWithIdentifier(Controller);

            ret = con;
        } catch (Exception ex) {
            ret = ex;
        }

        return ret;

    }


}

}