I assume you mean that you have 10 drop down lists and you need code which differs only in which control they use as the source for the SQL statement? If so, then it is pretty easy: just send all teh drop down lists to the same vent handler and use the
sender
parameter to determine which control it is:
DropDownList ddl = sender as DropDownList;
if (ddl != null)
{
SqlDataAdapter da4 = new SqlDataAdapter("select * from vehicle_category where vehicle_name='" + ddl.SelectedItem.ToString() + "' ", con);
...
If that isn't your problem, then you need to explain in more detail what you are having problems with.