CompilationErrorException: "cannot convert from" own type when passing value in method under CSharpScript

I am currently trying C# scripting and I have error as below when Test.DoThat method is called. If I change the DoThat method to without parameter then it is o.k. Please help.

Microsoft.CodeAnalysis.Scripting.CompilationErrorException: '(1,8): error CS1503: Argument 1: cannot convert from 'Scripting.Device [Scripting, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]' to 'Scripting.Device [C:\Users\sheehou\Documents\Code\Scripting\Scripting\bin\Debug\Scripting.exe]''

Here is my program:

using System;
using Microsoft.CodeAnalysis.Scripting;
using Microsoft.CodeAnalysis.CSharp.Scripting;

namespace Scripting
{
    public class Device
    {
        public string GetMessage()
        {
            return "Device";
        }
    }

    public class Test
    {
        public void DoThat(Device dev)
        {
            Console.WriteLine(dev.GetMessage());
        }
    }

    class Program6
    {
        static void Main(string[] args)
        {
            var test = new Test();

            var options = ScriptOptions.Default.AddReferences(typeof(Test).Assembly);
            var state = CSharpScript.RunAsync("", options, test, typeof(Test)).Result;
            state = state.ContinueWithAsync("using Scripting;").Result;
            state = state.ContinueWithAsync("Device dev = new Device();").Result;
            state = state.ContinueWithAsync("DoThat(dev);").Result;
            Console.Read();
        }
    }
}