Pass a username from a page to a user control

Hi All,

I've just started out with WPF and I need to pass a username/emailID from a WPF login window into a User control. The application opens with just the login screen and when authentication succeeds a winMain window is opened. Since I don't want to have several windows opening up, inside this winMain window I have a grid holder which will display 5 User Controls on button click events where some database operations are performed. 

I can easily pass the username from the login window to the winMain window, however I cannot work out how to pass it to the individual user control pages. I've tried some of the examples around however my username string is always empty within the User controls. Does anyone know of a simple solution I could try. 

Thanks

Denis