private void BtnEquals_Click(object sender, RoutedEventArgs e) { if (lastNumber != 0) { if (newNumber == 0) { newNumber = Convert.ToDouble(lblResult.Content.ToString()); } switch (selectedOperator) { case SelectedOperator.Multiplication: lblResult.Content = SimpleMath.Multiplicate(lastNumber, newNumber); break; case SelectedOperator.Substraction: lblResult.Content = SimpleMath.Sustract(lastNumber, newNumber); break; case SelectedOperator.Addition: lblResult.Content = SimpleMath.Add(lastNumber, newNumber); break; case SelectedOperator.Division: lblResult.Content = SimpleMath.Divide(lastNumber, newNumber); break; } lastNumber = Convert.ToDouble(lblResult.Content.ToString()); newNumber = 0; } }