父类对象和子类对象之间的转换

ChinesePersion entity = new ChinesePersion();
entity.RowUid = "ChinesePersion";

Persion user = entity; // user.RowUid = "ChinesePersion"

Persion p = new Persion();
p.RowUid = "Persion";

ChinesePersion cp = p as ChinesePersion; // cp = null