private void n5_KeyDown(object sender, KeyEventArgs e) { var temp = (sender as TextBox); if (e.Key == Key.Enter) { if (temp.Text == string.Empty) { Fourier.Cleare(5); } else { int.TryParse(temp.Text, out int v); Fourier.Draw(ffff.FourierSeries(v), -10, 10, 0.01, 5); } } }