Save RadioButton checked value into Database in ASP.Net

Hi 

I have 4 radiobutton in my page

1-RbtW

2-RbtE

3-RbtN

4-RbtS

i want if users checked RbtW it insert to database "West"

if checked RbtE it insert to database "East"

if checked RbtN it insert to database "North"

if checked RbtS it insert to database "Soutا"

HOw i can do it?

thanks