Getting your Silverlight application to show full screen is easy. Just set the following property:
Application.Current.Host.Content.IsFullScreen = true;
This property can only be set after a user-action, like a mouse click or button click. Setting the IsFullScreen property in the OnLoad of your Silverlight application won't work. Silverlight will ignore this.
I am developing silverlight app, for displaying flight information on public screens. Is there any workaround to start applicaton in full screen (without user interaction).
Not that I know of. But something you can do is run the browser in full screen mode (Shift+F11 for IE) on your public screens. Then make your Silverlight application 100% of the height and width of your browser window and you have the same effect. Good luck!