Multiple Portal in one Application

Hello I am developing one web forms application which supports multiple portals. Currently I have 2 Portals and I  created 2 folders 1. Fashion 2. Electronics Now links are 1. http://example.com/fashion 2. http://example.com/electronics But I want to create a facility to set one portal at a time. means when I set default is fashion then when I enter http://example.com the Fashion site will open and path is base path. When I set electronics as default then electronics site will be opened but path is base path (http://exmaple.com) Please anyone has idea how to do it???