Create subdomain programmatically

Question

Hi,

      I have a requirement like I just want to create a sub domain programmatically without using control panel.Now I have a registration form when the user creates an account ,based on his username I need to create a sub domain programatically for example my site url is http://www.example.com and after his successful registration he is going to get an url like this http://www.username.example.com .
                             How is it possible in .net can anybody help me to solve this problem.

Thanks in advance.