private IObservable <WeaponViewModel> AddWeaponImpl()
        {
            var weaponVm = new WeaponViewModel();

            Weapons.Add(weaponVm);

            return(Observable.Return(weaponVm));
        }
        private IObservable <WeaponViewModel> RemoveWeaponImpl(WeaponViewModel weaponVm)
        {
            Weapons.Remove(weaponVm);

            return(Observable.Return(weaponVm));
        }