How???

Asgharkhan

if there are 3 combobox for query

in 1st we chose a city

in 2nd combobox  city regions show and also execute query

in 3rd combobox show all streets of the current regions and also execute query

i confuse how this working?                            Jennifer Nery‌Dominique Broux‌ArcGIS API for Silverlight‌

this is example from 1 govt Site

1.png

AhmedEl-Sisi

You can do this using Query Task ,First you get All Cities via attribute query on cities layer and populate the returned features to cities combobox, then on combobox selection changed you get the related regions and streets via spatial query on regions and streets layers respectively using the geometry of selected city.

I think your snapshot is taken from Riyadh Interactive Map, you can monitor the requests using Fiddler or Firebug.