Program.cs

using System;

namespace @abstract  // learnt something here, how to handle a reserved word as a namespace, obviously a similar thing
{
    class Program
    {
        static void Main(string[] args)
        {
            var session = new Session();
            var builder = new DetailsViewModelBuilder();

            DisplayDetailsView(builder.AssembleFrom(session));
        }

        static void DisplayDetailsView(DetailsViewModel vm)
        {
            Console.WriteLine(vm.Data);
        }
    }

    internal abstract class ViewModelBuilder<T>
    {
        public abstract T AssembleFrom(Session session);
    }


    class DetailsViewModelBuilder : ViewModelBuilder<DetailsViewModel>
    {
        // pass in any dependencies required to assemble view model via ctor

        public override DetailsViewModel AssembleFrom(Session session)
        {
            throw new NotImplementedException();
        }
    }

    // Model 
    internal class Session
    {
        public Guid Id { get; set; }
    }

    // View Model
    internal class DetailsViewModel
    {
        public bool Data { get; set; }
    }
}