hi,
it means you have to tables in the database
bind your date of course table with first drop down as
dropdown1.datasource = your datasource
dropdown1.datatextfield= "name"
dropdown1.datavaluefield="id"
dropdown1.databind
then on the selected index changed of that dropdown
int i= Connvert.toInt32(ddl.selectedvalue)
on the basis of that id you can get record from your second table and bind that with your dropdown2