Calculator/Program.cs

using System.Diagnostics.Eventing.Reader;
using System.Windows.Forms;

namespace Calculator
{
    internal static class Program
    {
        static Form1 form = new Form1();
        static double valueA;
        static double valueB;
        static bool isSecondNumber = false;
        static bool answerGiven = false;
        static bool hasStoredAnwser = false;
        static double lastAnswer;
        static Operator selectedOperator;

        enum Operator
        {
            Add,
            Sub,
            Mult,
            Div
        }

        static void Main()
        {
            ApplicationConfiguration.Initialize();
            InitButtons();
            StartSelection();
            Application.Run(form);
        }

        static private void InitButtons()
        {
            form.btn_input_0.Click += RegisterInput;
            form.btn_input_1.Click += RegisterInput;
            form.btn_input_2.Click += RegisterInput;
            form.btn_input_3.Click += RegisterInput;
            form.btn_input_4.Click += RegisterInput;
            form.btn_input_5.Click += RegisterInput;
            form.btn_input_6.Click += RegisterInput;
            form.btn_input_7.Click += RegisterInput;
            form.btn_input_8.Click += RegisterInput;
            form.btn_input_9.Click += RegisterInput;

            form.btn_input_add.Click += SelectAdd;
            form.btn_input_sub.Click += SelectSub;
            form.btn_input_mult.Click += SelectMult;
            form.btn_input_div.Click += SelectDiv;

            form.btn_next.Click += Next;
            form.btn_import_prev.Click += ImportPrevious;
        }


        static private void ShowOperators(bool value)
        {
            form.btn_input_add.Visible = value;
            form.btn_input_sub.Visible = value;
            form.btn_input_mult.Visible = value;
            form.btn_input_div.Visible = value;
        }

        static private void ShowNumbers(bool value)
        {
            form.btn_input_0.Visible = value;
            form.btn_input_1.Visible = value;
            form.btn_input_2.Visible = value;
            form.btn_input_3.Visible = value;
            form.btn_input_4.Visible = value;
            form.btn_input_5.Visible = value;
            form.btn_input_6.Visible = value;
            form.btn_input_7.Visible = value;
            form.btn_input_8.Visible = value;
            form.btn_input_9.Visible = value;
            form.btn_import_prev.Visible = value;
        }

        static private void SelectAdd(object sender, EventArgs e)
        {
            OperatorSelected(Operator.Add);
        }
        static private void SelectSub(object sender, EventArgs e)
        {
            OperatorSelected(Operator.Sub);
        }
        static private void SelectMult(object sender, EventArgs e)
        {
            OperatorSelected(Operator.Mult);
        }
        static private void SelectDiv(object sender, EventArgs e)
        {
            OperatorSelected(Operator.Div);
        }

        static private void OperatorSelected(Operator operation)
        {
            form.lbl_main.Text = "Ange tal 1";
            ShowOperators(false);
            ShowNumbers(true);
            selectedOperator = operation;
            form.btn_next.Visible = false;
        }

        static private void StartSelection()
        {
            ShowOperators(true);
            isSecondNumber = false;
            answerGiven = false;
            form.lbl_main.Text = "V<>lj operation";
            form.btn_import_prev.Enabled = hasStoredAnwser;
        }

        static private void RegisterInput(object sender, EventArgs e)
        {
            if (sender is Button b)
            {
                form.lbl_number.Text += b.Text;
                form.btn_next.Visible = true;
            }
        }

        static private void ImportPrevious(object sender, EventArgs e)
        {
            form.lbl_number.Text += lastAnswer.ToString();
            form.btn_next.Visible = true;
        }

        static private void Next(object sender, EventArgs e)
        {
            if (answerGiven)
            {
                StartSelection();
                return;
            }

            if (!isSecondNumber)
            {
                valueA = double.Parse(form.lbl_number.Text);
                form.lbl_main.Text = "Ange tal 2";
                isSecondNumber = true;
                form.btn_next.Visible = false;
            }
            else
            {
                valueB = double.Parse(form.lbl_number.Text);
                Answer();
                isSecondNumber = false;
            }
            form.lbl_number.Text = "";
        }

        static private void Answer()
        {
            double value = 0;

            ShowOperators(false);
            ShowNumbers(false);

            if (selectedOperator == Operator.Add)
                value = valueA + valueB;
            else if (selectedOperator == Operator.Sub)
                value = valueA - valueB;
            else if (selectedOperator == Operator.Mult)
                value = valueA * valueB;
            else if (selectedOperator == Operator.Div)
                value = valueA / valueB;

            hasStoredAnwser = true;
            lastAnswer = value;
            form.btn_import_prev.Text = "Importera f<>reg<65>ende svar" + " (" + value.ToString() + ")";

            form.lbl_main.Text = "Ditt tal <20>r " + value.ToString();
            answerGiven = true;
        }
    }
}