Which Design Pattern - cascading dropdowns next screens

We have a web application built in .net 3.5 , C#


We have 2 cascading dropdowns.
First the parent dropdown ---> CountryNames
and Child dropdown -->Consists of list of states within the selected country

In the parent dropdown, there are P1,P2,P3,P4,P5 . For each value in the ParentDropDown , the Child_Dropdown will have 10 corresponding values


Based upon the values selected in the parent and child dropdowns , our plan is to show a webPage(Usercontrol) to the user. . Currently our application is built for only 1 value of Country --> India and State = Chandigarh ,Maharastra.

Now we want to extend our application to support 20 countries and the corresponding states , then which design pattern should we use ,? Would it be a good idea to use 1 usercontrol for each country and extend that user control for the states in the corresponding country or would it be better to have 1 user control for every state. I think it would be better to have 1 user control for each country and then extend that userControl for the corresponding states.

Pls see the attached image .

Which design pattern will help us ?



Please help.