Add project files.

Program.cs

@@ -0,0 +1,177 @@
+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;
+        }
+    }
+}