Acquire valid web url from Host.TopLevelDomain C#

Given a string which contains a partial url, for example "google.com"

Is it possible to get a valid URI from that string?

The expected result would be the same as you get from placing google.com in any web browsers address bar. Ex. http://www.google.com/

In the end I want ot pass this value to a new Uri object so I can use it in a HttpWebRequest to retrieve Favicons.