How can you change the startup page of SilevrLight application?

Answer:

Open the App.xaml.cs file

In the Application_Startup event handler, set the RootVisual property to the
instance of the particular SilverlIght class
example: if we have a file known as MainPage.xaml, a class known as MainPage will
be there in MainPage.xaml.cs.

private void Application_Startup(object sender, StartupEventArgs e)
{
this.RootVisual = new MainPage();
}