public override string ToString() { if (_gpu == null || _cpu == null || _motherboard == null || _sticker == null) { return(""); } var details = $"{_cpu.GetType().Name}: {_cpu.Cores} cores, {_cpu.Price}$\n{_gpu.GetType().Name}: {_gpu.Color} color, {_gpu.Price}$\n{_motherboard.GetType().Name}: {_motherboard.Size} size, {_motherboard.Price}$\n{_sticker.GetType().Name}: {_sticker.Hologram} hologram, {_sticker.Price}$"; return(details); }