creating webservice

http://chandradev819.wordpress.com/2...vice-and-ajax/

referrring to above for creating a WS for populating a listbox with some data

suppose i need to retrive country
i acn use select country from table
& execute & populate the listbox which i need from client side

the issue i am facing

1)public List FindAllCountries()
{
Error 1 Using the generic type 'System.Collections.Generic.List<T>' requires '1' type arguments

2) in the below query
select country from table

the column name is variable. i get the column name when a javascript is eexcute
how do i take that column name here

how do i get the name / pass the name in web service
in the script the name of the column is stored in a hidden field (H_CNAME)
i can reetrive this name in the cleint side javascript as weel as code behind
but how do i get

"select "+H_CNAME.value +" from table"