How To send a link on users mail

Question

Respected Experts
1)I need to do registration form in ASP.NET that I can do
2)when user submit form a link is to be send in users mail on mentioned mail address in registration form.
3)when user will open his mail and click on that click database will be reflected and then only he can be allowed get sign in as valid user in web site
Task no 2 and 3 I am not getting. Please help

Also In my company I have to develop website as magicbricks.com please suggest me what type study I should do to do that or what points should I learn in ASP.NET to get a good start.
Thanks