Unity bootstrapper errors WPF MVVM project

    public partial class App : Application
    {
        protected override void OnStartup(StartupEventArgs e)
        {
            base.OnStartup(e);
            //Error following line
            Bootstrapper bootstrapper = new Bootstrapper();
            //CS0144  Cannot create an instance of the abstract class or interface 'Bootstrapper'
            bootstrapper.Run();
        }
    }
}
//BOOTSTRAPPER has no build errors