What is the most efficient way to handle the lifecycle of an object with COM interop?

class Program
    {
        static void Main(string[] args)
        {
            using(WorkflowRuntime workflowRuntime = new WorkflowRuntime())
            {
                AutoResetEvent waitHandle = new AutoResetEvent(false);
                workflowRuntime.WorkflowCompleted += delegate(object sender, WorkflowCompletedEventArgs e)
                {
                    waitHandle.Set();
                };
                workflowRuntime.WorkflowTerminated += delegate(object sender, WorkflowTerminatedEventArgs e)
                {
                    Console.WriteLine(e.Exception.Message);
                    waitHandle.Set();
                };

                WorkflowInstance instance = workflowRuntime.CreateWorkflow(typeof(WorkflowConsoleApplication1.Workflow1));
                instance.Start();

                waitHandle.WaitOne();
            }
            Console.ReadKey();
        }
    }

public sealed partial class Workflow1: SequentialWorkflowActivity
    {
    	public Workflow1()
    	{
    		InitializeComponent();
            this.codeActivity1.ExecuteCode += new System.EventHandler(this.codeActivity1_ExecuteCode);
        }

        [DebuggerStepThrough()]
        private void codeActivity1_ExecuteCode(object sender, EventArgs e)
        {
            Console.WriteLine("Throw ApplicationException.");
            throw new ApplicationException();
        }

        protected override void Dispose(bool disposing)
        {
            if (disposing)
            {
                // Here you must free your resources
                // by calling your COM helper Dispose() method
                Console.WriteLine("Object disposed.");
            }
        }
    }

MyComHelper helper = new MyComHelper();
helper.DoStuffWithExcel();
helper.Dispose();
...

MyComHelper helper = new MyComHelper();
try
{
    helper.DoStuffWithExcel();
}
finally()
{
    helper.Dispose();
}

using(MyComHelper helper = new MyComHelper())
{
    helper.DoStuffWithExcel();
}