How to Select data field to display in drop down list ?

hi guys 

i have 2 tbls are below

 

1/(RegionTbl). 

 

Region id         PK 

RegionName  Nvarchar  

 

2/ (CityTbl)

 CityID

RegionID         Fk

CityName      Nvarchar  Pk 

 

and in application i have 2 dropdownlist , list1 is datasource from RegionTble To select RegionName and list 2 from CityName in order to seletc from list1 regionname to display cities in list2 as afilter data 

 

please give me solution step by step