ADO.NET :: Adding Data To Table Using Linq To Sql?

i am choosing a category from a DropDownList controll, and if want to add a new category at the same time i have a TextBoks for it, i have create a Model, BLL and DAL classes, my problem is:

in the DAL class i want to add a new row to Question, but i need to check first if the object.category exsist in the table Category, if it does i want to get the Cid for it if it dosen't exist i want to create a new raw then get the Cid, this is my code:

public string add(Faq inFaq)
{
using (var db = new DBClassDataContext())
{
try
{
var se = from Category in db.Categorys
where Category.category == inFaq.category
select Category.Cid;
if (se.Count() == 0 ).........