Open Dynamo in background while C# add-in executes

This may or may not help but I threw a stone in the dark as below:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Autodesk.Revit.DB;
using Autodesk.Revit.UI;
using Dynamo.Applications;
using Dynamo.Core;

namespace my_addin
{
    [Autodesk.Revit.Attributes.Transaction(Autodesk.Revit.Attributes.TransactionMode.Manual)]
    class DynamoTest : IExternalCommand
    {
        public Result Execute(ExternalCommandData commandData, ref string message, ElementSet elements)
        {


            string Journal_Dynamo_Path = path_to_my_dyn_file;
            DynamoRevit dynamoRevit = new DynamoRevit()

            DynamoRevitCommandData dynamoRevitCommandData = new DynamoRevitCommandData();
            dynamoRevitCommandData.Application = commandData.Application;
            IDictionary<string, string> journalData = new Dictionary<string, string>
            {
                { Dynamo.Applications.JournalKeys.AutomationModeKey, true.ToString() },
                { Dynamo.Applications.JournalKeys.ShowUiKey, false.ToString() },
                { Dynamo.Applications.JournalKeys.DynPathKey, Journal_Dynamo_Path }
            };
            dynamoRevitCommandData.JournalData = journalData;       

            Result externalCommandResult = dynamoRevit.ExecuteCommand(dynamoRevitCommandData);

            return externalCommandResult;



        }
    }
}

And I’m getting this error:

image

Does anyone know what I’m doing wrong?