Apply theme programmatically Sharepoint 2010

We can manage the theme from UI of Sharepoint also but sometimes we have a requirement like we need to manage theme through a feature i.e. on feature activation we need to apply some theme and on deactivation remove that theme and apply the default no-theme of Sharepoint.
Add the Microsoft.SharePoint.Utilities reference.

http://www.directsharepoint.com/2011/03/programmatically-apply-theme-to-web-in.html