FileStream操作写入空文件

我有一个ASP.Net MVC 4应用程序正在下载一个空文件。我错过了什么？

控制器：

public class HomeController : Controller
{
    public ActionResult Index()
    {
        return View();
    }
    public FileStreamResult ICS()
    {
        var memoryStream = new MemoryStream();
        StreamWriter sw = new StreamWriter(memoryStream);
        sw.WriteLine(@"BEGIN:VCALENDAR");
        sw.WriteLine(@"VERSION:2.0");
        sw.WriteLine(@"PRODID:-//www.marudot.com//iCal Event Maker");
        sw.WriteLine(@"BEGIN:VEVENT");
        sw.WriteLine(@"DTSTAMP:20141111T165545Z");
        sw.WriteLine(@"UID:20141111T165545Z-1194755835@marudot.com");
        sw.WriteLine(@"DTSTART;TZID=""America/Chicago"":20141114T080000");
        sw.WriteLine(@"DTEND;TZID=""America/Chicago"":20141114T120000");
        sw.WriteLine(@"SUMMARY:Bobby's Big Bash");
        sw.WriteLine(@"DESCRIPTION:test");
        sw.WriteLine(@"LOCATION:test");
        sw.WriteLine(@"END:VEVENT");
        sw.WriteLine(@"END:VCALENDAR");
        sw.Flush();
        return new FileStreamResult(memoryStream, "text/calendar") { FileDownloadName = "test.ics" };
    }
}

视图：

<h2>Index</h2>
@Html.ActionLink("ical event", "ICS");

单击链接下载一个空的ICS文件。