private void Button_Click_Equals(object sender, RoutedEventArgs e)
        {
            var equation = OperationBox.Text + InputBox.Text;

            var result = CalcController.CalculateResult(equation);

            if (result != null)
            {
                CalcController.OverwriteInput(result);
                CalcController.ClearOperationBox();
            }
            else
            {
                CalcController.ClearAll();
            }
        }