Parsing/getting data from a website (with authentication)

Hi!
In my PCL app I need to get some data from a website who requires authentication (login), and then parse them and the data I need in a page.
I'd like to understand which is the best way to achieve this.

I downloaded some some apps that show the login page of the website in a webview and then, after the authentication successes, the (parsed) data (of this website) are shown in a typical page.
Is this the best and safest way? How it works?

Thanks to all