Membuat Aplikasi Kalkulator dengan VB.NET (Source Code Lengkap)

Imports System.Globalization
Imports System.Linq
Imports System.Windows.Forms

Public Module Kalkulator

    ' Mengubah teks menjadi angka. Menerima koma maupun titik sebagai pemisah desimal.
    Public Function BacaAngka(teks As String, ByRef nilai As Double) As Boolean
        Return Double.TryParse(teks.Trim().Replace(",", "."), NumberStyles.Float,
                               CultureInfo.InvariantCulture, nilai)
    End Function

    ' Menghitung hasil operasi. Sin/Cos/Tan/Akar/Log hanya memakai Bilangan 1.
    Public Function Hitung(b1 As Double, b2 As Double, operasi As String) As String
        Select Case operasi
            Case "Tambah" : Return (b1 + b2).ToString()
            Case "Kurang" : Return (b1 - b2).ToString()
            Case "Kali" : Return (b1 * b2).ToString()
            Case "Bagi"
                If b2 = 0 Then Return "Tidak bisa dibagi nol"
                Return (b1 / b2).ToString()
            Case "Mod"
                If b2 = 0 Then Return "Tidak bisa dibagi nol"
                Return (b1 Mod b2).ToString()
            Case "Pangkat" : Return Math.Pow(b1, b2).ToString()
            Case "Akar"
                If b1 < 0 Then Return "Akar bilangan negatif tidak terdefinisi"
                Return Math.Sqrt(b1).ToString()
            Case "Sin" : Return Math.Round(Math.Sin(b1 * Math.PI / 180), 4).ToString()
            Case "Cos" : Return Math.Round(Math.Cos(b1 * Math.PI / 180), 4).ToString()
            Case "Tan" : Return Math.Round(Math.Tan(b1 * Math.PI / 180), 4).ToString()
            Case "Log"
                If b1 <= 0 Then Return "Log hanya untuk bilangan positif"
                Return Math.Round(Math.Log10(b1), 4).ToString()
            Case "Compare"
                If b1 > b2 Then Return "Bilangan 1 lebih besar"
                If b1 < b2 Then Return "Bilangan 2 lebih besar"
                Return "Kedua bilangan sama"
            Case Else
                Return "Operasi tidak dikenal"
        End Select
    End Function

    ' Membaca input dari form, memvalidasi, lalu menampilkan hasil. Dipakai oleh ketiga form.
    Public Sub Proses(txtBil1 As TextBox, txtBil2 As TextBox, txtHasil As TextBox, operasi As String)
        Dim b1, b2 As Double

        If Not BacaAngka(txtBil1.Text, b1) Then
            MessageBox.Show("Bilangan 1 harus berupa angka.", "Input tidak valid",
                            MessageBoxButtons.OK, MessageBoxIcon.Warning)
            txtBil1.Focus()
            Return
        End If

        ' Sin, Cos, Tan, Akar, dan Log hanya butuh Bilangan 1
        Dim cukupSatu As Boolean = {"Sin", "Cos", "Tan", "Akar", "Log"}.Contains(operasi)
        If Not cukupSatu AndAlso Not BacaAngka(txtBil2.Text, b2) Then
            MessageBox.Show("Bilangan 2 harus berupa angka.", "Input tidak valid",
                            MessageBoxButtons.OK, MessageBoxIcon.Warning)
            txtBil2.Focus()
            Return
        End If

        txtHasil.Text = Hitung(b1, b2, operasi)
    End Sub

End Module

Public Class Kalkulator1

    ' Satu handler untuk semua tombol operasi. Nama operasi disimpan di properti Tag tiap tombol.
    Private Sub Operasi_Click(sender As Object, e As EventArgs) Handles _
            btnTambah.Click, btnKurang.Click, btnKali.Click, btnBagi.Click,
            btnPangkat.Click, btnSin.Click, btnCos.Click, btnTan.Click,
            btnAkar.Click, btnLog.Click, btnCompare.Click, btnMod.Click

        Dim tombol As Button = DirectCast(sender, Button)
        Proses(txtBil1, txtBil2, txtHasil, tombol.Tag.ToString())
    End Sub

    Private Sub btnClean_Click(sender As Object, e As EventArgs) Handles btnClean.Click
        txtBil1.Clear()
        txtBil2.Clear()
        txtHasil.Clear()
        txtBil1.Focus()
    End Sub

    Private Sub btnExit_Click(sender As Object, e As EventArgs) Handles btnExit.Click
        Close()
    End Sub

End Class

Public Class Kalkulator2

    Private Sub Kalkulator2_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        cboProses.DropDownStyle = ComboBoxStyle.DropDownList   ' pengguna tidak bisa mengetik bebas
        cboProses.Items.AddRange(New Object() {
            "Tambah", "Kurang", "Kali", "Bagi", "Pangkat", "Mod",
            "Akar", "Sin", "Cos", "Tan", "Log", "Compare"})
    End Sub

    Private Sub cboProses_SelectedIndexChanged(sender As Object, e As EventArgs) _
            Handles cboProses.SelectedIndexChanged
        If cboProses.SelectedIndex >= 0 Then
            Proses(txtBil1, txtBil2, txtHasil, cboProses.Text)
        End If
    End Sub

    Private Sub btnClean_Click(sender As Object, e As EventArgs) Handles btnClean.Click
        txtBil1.Clear()
        txtBil2.Clear()
        txtHasil.Clear()
        cboProses.SelectedIndex = -1
    End Sub

    Private Sub btnExit_Click(sender As Object, e As EventArgs) Handles btnExit.Click
        Close()
    End Sub

End Class

Public Class Kalkulator3

    ' CheckedChanged terpanggil dua kali saat pilihan berpindah (yang lama & yang baru),
    ' jadi hanya proses RadioButton yang sedang tercentang.
    Private Sub Radio_CheckedChanged(sender As Object, e As EventArgs) Handles _
            rbTambah.CheckedChanged, rbKurang.CheckedChanged, rbKali.CheckedChanged,
            rbBagi.CheckedChanged, rbPangkat.CheckedChanged, rbAkar.CheckedChanged,
            rbMod.CheckedChanged, rbSin.CheckedChanged, rbCos.CheckedChanged,
            rbTan.CheckedChanged, rbLog.CheckedChanged, rbCompare.CheckedChanged

        Dim rb As RadioButton = DirectCast(sender, RadioButton)
        If rb.Checked Then
            Proses(txtBil1, txtBil2, txtHasil, rb.Tag.ToString())
        End If
    End Sub

    Private Sub btnClean_Click(sender As Object, e As EventArgs) Handles btnClean.Click
        txtBil1.Clear()
        txtBil2.Clear()
        txtHasil.Clear()
        For Each rb In grpProses.Controls.OfType(Of RadioButton)()
            rb.Checked = False
        Next
    End Sub

    Private Sub btnExit_Click(sender As Object, e As EventArgs) Handles btnExit.Click
        Close()
    End Sub

End Class