Linq to Entities - 使用主键增加列

I have this code:

我有这个代码:

    Message message = new Message();
    message.Id = 5;
    message.EntityKey = context.CreateEntityKey("MessageSet", entity);
    message.Votes++;
    context.Attach(entity);
    context.ObjectStateManager.GetObjectStateEntry(entity.EntityKey).SetModifiedProperty("Votes");
    Save();
    Message messa