Windows standard calulator replica in WinForms C#

By Posted on

Problem

I tried my best to replicate, in style and functionality, the Windows standard calculator:

I would like to get some feedback on the efficiency and readability of my code as well as the approach i chose (for example the one of using the evaluate function on the expression textbox):

Form1.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;


namespace _2022_01_27
{
    public partial class Form1 : Form
    {
        bool equals_last_pressed;
        double last_number_entry = 0;
        public Form1()
        {
            InitializeComponent();
        }

        private void Add_to_entry(string digit)
        {
            if (tbox_entry.Text.Length <= 18)
            {
                tbox_entry.Text += digit;
                tbox_entry.Text = Convert.ToString(double.Parse(tbox_entry.Text));
            }
            equals_last_pressed = false;
        }

        static Double Evaluate(String expression)
        {
            System.Data.DataTable table = new System.Data.DataTable();
            return Convert.ToDouble(table.Compute(expression, String.Empty));
        }

        private void btn_0_Click(object sender, EventArgs e)
        {
            Add_to_entry("0");
        }

        private void btn_1_Click(object sender, EventArgs e)
        {
            Add_to_entry("1");
        }

        private void btn_2_Click(object sender, EventArgs e)
        {
            Add_to_entry("2");
        }

        private void btn_3_Click(object sender, EventArgs e)
        {
            Add_to_entry("3");
        }

        private void btn_4_Click(object sender, EventArgs e)
        {
            Add_to_entry("4");
        }

        private void btn_5_Click(object sender, EventArgs e)
        {
            Add_to_entry("5");
        }

        private void btn_6_Click(object sender, EventArgs e)
        {
            Add_to_entry("6");
        }

        private void btn_7_Click(object sender, EventArgs e)
        {
            Add_to_entry("7");
        }

        private void btn_8_Click(object sender, EventArgs e)
        {
            Add_to_entry("8");
        }

        private void btn_9_Click(object sender, EventArgs e)
        {
            Add_to_entry("9");
        }

        private void btn_c_Click(object sender, EventArgs e)
        {
            tbox_entry.Text = "0";
            tbox_expression.Text = "";
            last_number_entry = 0;
        }

        private void btn_ce_Click(object sender, EventArgs e)
        {
            tbox_entry.Text = "0";
        }

        private void btn_backspace_Click(object sender, EventArgs e)
        {
            tbox_entry.Text = tbox_entry.Text.Remove(tbox_entry.Text.Length - 1);
            if (tbox_entry.Text.Length == 0)
                tbox_entry.Text = "0";
        }

        private void btn_addition_Click(object sender, EventArgs e)
        {
            last_number_entry = double.Parse(tbox_entry.Text);
            if (equals_last_pressed == false)
                tbox_expression.Text += tbox_entry.Text;
            tbox_expression.Text = $"{Evaluate(tbox_expression.Text)} + ";
            tbox_entry.Text = "0";
            equals_last_pressed = false;
        }

        private void btn_subtraction_Click(object sender, EventArgs e)
        {
            last_number_entry = double.Parse(tbox_entry.Text);
            if (equals_last_pressed == false)
                tbox_expression.Text += tbox_entry.Text;
            tbox_expression.Text = $"{Evaluate(tbox_expression.Text)} - ";
            tbox_entry.Text = "0";
            equals_last_pressed = false;
        }

        private void btn_multiplication_Click(object sender, EventArgs e)
        {
            last_number_entry = double.Parse(tbox_entry.Text);
            if (equals_last_pressed == false)
                tbox_expression.Text += tbox_entry.Text;
            tbox_expression.Text = $"{Evaluate(tbox_expression.Text)} * ";
            tbox_entry.Text = "0";
            equals_last_pressed = false;
        }

        private void btn_division_Click(object sender, EventArgs e)
        {
            last_number_entry = double.Parse(tbox_entry.Text);
            if (equals_last_pressed == false)
                tbox_expression.Text += tbox_entry.Text;
            tbox_expression.Text = $"{Evaluate(tbox_expression.Text)} / ";
            tbox_entry.Text = "0";
            equals_last_pressed = false;
        }

        private void btn_sqrtx_Click(object sender, EventArgs e)
        {
            tbox_entry.Text = $"{Math.Sqrt(double.Parse(tbox_entry.Text))}";
        }

        private void btn_x2_Click(object sender, EventArgs e)
        {
            tbox_entry.Text = $"{Math.Pow(double.Parse(tbox_entry.Text), 2)}";
        }

        private void btn_1dividex_Click(object sender, EventArgs e)
        {
            if (tbox_entry.Text == "0")
                return;
            tbox_entry.Text = $"{1 / double.Parse(tbox_entry.Text)}";
        }

        private void btn_equals_Click(object sender, EventArgs e)
        {
            last_number_entry = double.Parse(tbox_entry.Text);
            if (equals_last_pressed == true)
                return;
            equals_last_pressed = true;
            tbox_expression.Text += $"{tbox_entry.Text}";
            tbox_entry.Text = Convert.ToString(Evaluate(tbox_expression.Text));
        }

        private void btn_period_Click(object sender, EventArgs e)
        {
            foreach(char digit in tbox_entry.Text)
                if (digit == '.')
                    return;
            tbox_entry.Text += ".";
        }

        private void btn_changesign_Click(object sender, EventArgs e)
        {
            if (tbox_entry.Text.Contains("-"))
                tbox_entry.Text = tbox_entry.Text.Remove(0,1);
            else
                tbox_entry.Text = "-" + tbox_entry.Text;
        }

        private void btn_percentage_Click(object sender, EventArgs e)
        {
            tbox_entry.Text = Convert.ToString(last_number_entry / 100 * double.Parse(tbox_entry.Text));
        }
    }
}

Solution

Since aepot has already mentioned a way how can you reduce the code of the btn_{n}_Click event handlers so, I will not address that problem here.

Add_to_entry

  • I think the second tbox_entry.Text assignment is pointless
  • This piece of code double.Parse(tbox_entry.Text) is being used in several places I suggest to introduce a helper method for that
private double GetEntryAsNumber()
    => double.Parse(tbox_entry.Text);

Evaluate

  • According to my understanding you don’t need to create a new Table each and every time when you call this method
  • So, you can convert the table to a static member of the class
static System.Data.DataTable table = new System.Data.DataTable();
static double Evaluate(string expression)
    => Convert.ToDouble(table.Compute(expression, string.Empty));

btn_c_Click and btn_ce_Click

  • This code tbox_entry.Text = "0" is being used in multiple places so you can define a helper method for this
private void SetEntryToZero()
    => tbox_entry.Text = "0";

private void btn_c_Click(object sender, EventArgs e)
{
    SetEntryToZero();
    tbox_expression.Text = "";
    last_number_entry = 0;
}

private void btn_ce_Click(object sender, EventArgs e)
    => SetEntryToZero();

btn_addition_Click … btn_division_Click

  • As I can see their code are almost identical except that part which comes after the Evaluate call, so the common part can be extracted
private void btn_addition_Click(object sender, EventArgs e)
    => PrepareForTheSecondOperand("+");

private void btn_subtraction_Click(object sender, EventArgs e)
    => PrepareForTheSecondOperand("-");

private void btn_multiplication_Click(object sender, EventArgs e)
    => PrepareForTheSecondOperand("*");

private void btn_division_Click(object sender, EventArgs e)
    => PrepareForTheSecondOperand("/");
    
private void PrepareForTheSecondOperand(string operation)
{
    last_number_entry = GetEntryAsNumber();
    if (!equals_last_pressed)
        tbox_expression.Text += tbox_entry.Text;
    tbox_expression.Text = $"{Evaluate(tbox_expression.Text)} {operation} ";
    SetEntryToZero();
    equals_last_pressed = false;
}
  • Instead of using the == false you can simply use the negation operator

btn_sqrtx_Click … btn_1dividex_Click

  • All three methods can be implemented as a one-liner
    • In case of 1dividex you can use the conditional operator
private void btn_sqrtx_Click(object sender, EventArgs e)
    => tbox_entry.Text = $"{Math.Sqrt(GetEntryAsNumber())}";

private void btn_x2_Click(object sender, EventArgs e)
    => tbox_entry.Text = $"{Math.Pow(GetEntryAsNumber(), 2)}";
        
private void btn_1dividex_Click(object sender, EventArgs e)
    => tbox_entry.Text = tbox_entry.Text == "0" ? tbox_entry.Text : $"{1 / GetEntryAsNumber()}";

btn_equals_Click

  • Two minor things:
    • You don’t need to use string interpolation when you do the assignment for tbox_expression.Text
    • You don’t need to use Convert.ToString static method, you can simply call the ToString instance method on the double
private void btn_equals_Click(object sender, EventArgs e)
{
    last_number_entry = GetEntryAsNumber();
    if (equals_last_pressed)
        return;
    equals_last_pressed = !equals_last_pressed;
    tbox_expression.Text += tbox_entry.Text;
    tbox_entry.Text = Evaluate(tbox_expression.Text).ToString();
}

btn_period_Click, btn_changesign_Click and btn_percentage_Click

  • All three methods can be implemented as a one-liner
    • In case of period you can use Linq’s Any to find a dot
    • In case of changesign you can use conditional operator
private void btn_period_Click(object sender, EventArgs e)
    => tbox_entry.Text += tbox_entry.Text.ToCharArray().Any(c => c == '.') ? "" : ".";

private void btn_changesign_Click(object sender, EventArgs e)
    => tbox_entry.Text = tbox_entry.Text.Contains("-") ? tbox_entry.Text.Remove(0, 1): "-" + tbox_entry.Text;
        
private void btn_percentage_Click(object sender, EventArgs e)
    => tbox_entry.Text = Convert.ToString(last_number_entry / 100 * GetEntryAsNumber());

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