[E2010] [EWSMA] [C#] Convert FolderEntryId to FolderId

I have PidTagWlinkEntryIdfrom "Navigation shortcuts" http://msdn.microsoft.com/en-us/library/ee179467(v=exchg.80).aspx in this "Folder EntryID Structure" http://msdn.microsoft.com/en-us/library/ee217297(v=exchg.80).aspx. How can I convert this to FolderId http://msdn.microsoft.com/en-us/library/dd633930(v=exchg.80).aspx?

When I try to do the following:

var appointments = service.FindAppointments(
    new FolderId(Convert.ToBase64String(entryId)),
    new CalendarView(DateTime.Now.Date, DateTime.Now.Date.AddDays(7)));

i get this Exception:

[Microsoft.Exchange.WebServices.Data.ServiceResponseException] = {"Id is malformed."}

Any help would be appreciated.

Thanks in advance.