使用Bloomberg API时，会话未在c#中启动

我正在做Bloomberg API，我遵循了这个教程

http://holowczak.com/bloomberg-api-csharp-rr/11/

但是我得到错误

InvalidOperationException未处理:Session not started at line result = Session . openservice ("//blp/refdata");

我是彭博的新手，想要使用它的API，所以请告诉我如何纠正这些错误。下面是我的代码。由于

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Bloomberglp.Blpapi;
namespace Bloomberg
{
    class Program
    {
        static void Main(string[] args)
        {
            bool result;
            bool done = false;
            SessionOptions sessionOptions = new SessionOptions();
            sessionOptions.ServerHost = "localhost";
            sessionOptions.ServerPort = 8194;
            Session session = new Session(sessionOptions);
            result = session.Start();
            result = session.OpenService("//blp/refdata");
            Service referenceService = session.GetService("//blp/refdata");
            Request request = referenceService.CreateRequest("HistoricalDataRequest");
            request.Append("securities", "IBM US Equity");
            request.Append("fields", "PX_LAST");
            request.Set("startDate", "20130601");
            request.Set("endDate", "20130630");
            request.Set("maxDataPoints", 20);
            session.SendRequest(request, null);
            done = false;
            while (!done)
            {
                Event eventObject = session.NextEvent();
                if (eventObject.Type == Event.EventType.RESPONSE)
                {
                    foreach (Message msg in eventObject)
                    {
                        System.Console.WriteLine(msg);
                    }
                    done = true;
                } 
            } 
            Console.ReadKey();
            session.Stop();
        }
    } 
}