动态选择列表C＃

Question

I have three listboxes in windowsform app. I want to display the countries, states, cities in respective three listboxes. But the states should be displayed according to the country selected and similarly for the cities.

Now the code may not seem an issue for two three countries, but what if I take a practical situation keeping in mind all countries of the world and their corresponding states and cities.

What will be the best way to implement this ?

Update --- I actually wanted to ask what data structures will be best for this ?
A 3d jagged array wiil work fine .nO ? or are there any better ways to do this ? i have no idea how to do this . Can anyone code this ?

Answer 1

load all the countries into the first list. when the user selects a country clear the state/providence and city list boxes. load the cities for the select state/providence. when a state/providence is selected load the cities.

additional options:

1. have the user enter their postal code (assuming there are international code) and lookup up the city based on the code.
2. allow the user to enter this into free form text boxes instead of a predefined list.
3. require the user to enter the first N characters before populating the list with matching choices.

Answer 2

Generally a top down hierarchy is applied.

1. Bind the countries list (nothing else)
2. On country selection, bind/rebind the states list filtered for the country & clear the city list.
3. Finally on a state selection, bind/rebind the city dropdown.