1
It's better for DOJO to make a widget just like "CaseCadingDropDown" in MicroSoft-Asp.net's AjaxToolkit.
We know , we always have to make two "" or more when we want to make "Country-Town-Street-PostCode" select .
So why don't we just make a widigt called "CaseCadingDropDown" like MicroSoft called ?
I think this widigit will be very helpful , I have found so many questions about "How to make FilterSelect dynamic" in this forum.

2
The "ItemFileReadSotre" must be extended.
Right now , I use "FilterSelect" and "ItemFileReadSotre" to make my "CaseCadingDropDown" ,
I select the first "FilterSelect" , then the client sends something to the server , the server searches data from the database and then forms one "JOSN TYPE" output, then the server sends something to the client's "ItemFileReadSotre" which is connected to another "FilterSelect" , so that another "FilterSelect" lists options related to the first "FilterSelect".

Well , It seems that my "CaseCadingDropDown" works well ~~~ And yes , it is , but only when I only use English.
I'm a Chinese student , my chum mocked my demo because it don't support Chinese character.
If I want to use Chinese , there are the problems :
JSON can't support Chinese directly , I must use utf8.
ItemFileReadStore don't support utf8 ! So I must write another class by myself to replace the ItemFileReadStore,well , I boasted ,I have not succed in finish this very class yet.

I hope DOJO extends the ItemFileReadSotre , to make it support Chinese character.