private static int cont = 2;
public static boolean esPrimo(int num) {
		byte aux = 0;
		if (num % cont == 0) {
			aux = 0;
		} else {
			aux = 1;
			esPrimo(num-1);
		}
		if (aux == 0) {
			return false;
		} else {
			return true;
		}

	}

Public Class Form1
    Dim tipo, base As Byte
    Dim todo As Boolean
    Dim num1, num2, num, total As Double
    Dim operador As String
    Dim totalh As String
    ' función que convierte de número Hexadecimal a Decimal  
    ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''  
    Public Function HexToDec(ByVal HexStr As String) As Double
        Dim mult As Double
        Dim DecNum As Double
        Dim ch As String
        mult = 1
        DecNum = 0
        Dim i As Integer
        For i = Len(HexStr) To 1 Step -1
            ch = Mid(HexStr, i, 1)
            If (ch >= "0") And (ch <= "9") Then
                DecNum = DecNum + (Val(ch) * mult)
            Else
                If (ch >= "A") And (ch <= "F") Then
                    DecNum = DecNum + ((Asc(ch) - Asc("A") + 10) * mult)
                Else
                    If (ch >= "a") And (ch <= "f") Then
                        DecNum = DecNum + ((Asc(ch) - Asc("a") + 10) * mult)
                    Else
                        HexToDec = 0
                        Exit Function
                    End If
                End If
            End If
            mult = mult * 16
        Next i
        HexToDec = DecNum
    End Function
    ' función que convierte de número Decimal a Hexadecimal  
    ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''  
    Public Function DecToHex(ByVal DecNum As Double) As String
        Dim remainder As Integer
        Dim HexStr As String
        HexStr = ""
        Do While DecNum <> 0
            remainder = DecNum Mod 16
            If remainder <= 9 Then
                HexStr = Chr(Asc(remainder)) & HexStr
            Else
                HexStr = Chr(Asc("A") + remainder - 10) & HexStr
            End If
            DecNum = DecNum \ 16
        Loop
        If HexStr = "" Then HexStr = "0"
        DecToHex = HexStr
    End Function
    ' función que convierte de número Decimal a Binario  
    ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''  
    Public Function DecToBin(ByVal DecNum As Double) As String
        Dim BinStr As String
        BinStr = ""
        Do While DecNum <> 0
            If (DecNum Mod 2) = 1 Then
                BinStr = "1" & BinStr
            Else
                BinStr = "0" & BinStr
            End If
            DecNum = DecNum \ 2
        Loop
        If BinStr = "" Then BinStr = "0000"
        DecToBin = BinStr
    End Function
    ' función que convierte de número Binario a número decimal  
    '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''  
    Public Function BinToDec(ByVal BinStr As String) As Double
        Dim mult As Double
        Dim DecNum As Double
        mult = 1
        DecNum = 0
        Dim i As Integer
        For i = Len(BinStr) To 1 Step -1
            If Mid(BinStr, i, 1) = "1" Then
                DecNum = DecNum + mult
            End If
            mult = mult * 2
        Next i
        BinToDec = DecNum
    End Function
    ' función que convierte de número Hexadecimal a número binario  
    ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''  
    Public Function HexToBin(ByVal HexStr As String) As String
        Dim BinStr As String
        BinStr = ""
        Dim i As Integer
        For i = 1 To Len(HexStr)
            BinStr = BinStr & DecToBin(HexToDec(Mid(HexStr, i, 1)))
        Next i
        HexToBin = BinStr
    End Function
    ' función que convierte de número binario a Hexadecimal  
    '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''  
    Public Function BinToHex(ByVal BinStr As String) As String
        Dim HexStr As String
        HexStr = ""
        Dim i As Integer
        For i = 1 To Len(BinStr) Step 4
            HexStr = HexStr & DecToHex(BinToDec(Mid(BinStr, i, 4)))
        Next i
        BinToHex = HexStr
    End Function
    ' función que convierte de número octal a decimal  
    ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
    Public Function octToDec(ByVal octStr As String) As String
        Dim digitos, numero, resultado As Double
        digitos = Len(num)
        For cuenta = 1 To digitos
            numero = Mid(num, cuenta, 1)
            resultado = resultado + numero * 8 ^ (digitos - cuenta)
        Next cuenta
        octToDec = resultado
    End Function
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Me.Height = 281
        Me.Width = 256
        todo = False
        Me.MaximizeBox = False
        Me.MinimizeBox = False
        Me.FormBorderStyle = Windows.Forms.FormBorderStyle.FixedSingle
        Me.Text = "Calculadora"
        RadioButton1.Checked = True
        'Button25.Enabled = False
        'Button24.Enabled = False
        'Button23.Enabled = False
        'Button22.Enabled = False
        'Button21.Enabled = False
        base = 10
    End Sub
    Private Sub Button20_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button20.Click
        If todo = False Then
            Me.Height = 281
            Me.Width = 415
            todo = True
        Else
            Me.Height = 281
            Me.Width = 256
            todo = False
        End If
    End Sub
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click, Button2.Click, Button3.Click, Button4.Click, Button5.Click, Button6.Click, Button7.Click, Button8.Click, Button9.Click, Button10.Click, Button12.Click, Button25.Click, Button24.Click, Button23.Click, Button22.Click, Button21.Click
        TextBox1.Text &= sender.text
    End Sub
    Private Sub Button27_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button27.Click
        TextBox1.Clear()
    End Sub
    Private Sub Button26_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button26.Click
        TextBox1.Clear()
        num1 = 0
        num2 = 0
        total = 0
    End Sub
    Private Sub Button15_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button15.Click, Button14.Click, Button13.Click, Button11.Click, Button19.Click, Button18.Click, Button17.Click, Button16.Click
        Select Case sender.text
            Case "/"
                tipo = 1
                num1 = CDbl(TextBox1.Text)
                TextBox1.Clear()
            Case "x"
                tipo = 2
                num1 = CDbl(TextBox1.Text)
                TextBox1.Clear()
            Case "+"
                tipo = 3
                num1 = CDbl(TextBox1.Text)
                TextBox1.Clear()
            Case "-"
                tipo = 4
                num1 = CDbl(TextBox1.Text)
                TextBox1.Clear()
            Case "1/x"
                tipo = 5
                num1 = CDbl(TextBox1.Text)
                TextBox1.Text = 1 / num1
            Case "Log"
                tipo = 6
                num1 = CDbl(TextBox1.Text)
                TextBox1.Text = Math.Log10(num1)
            Case "√"
                tipo = 7
                num1 = 1 / CDbl(TextBox1.Text)
                TextBox1.Clear()
        End Select
    End Sub
    Private Sub Button16_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button16.Click
        num2 = CDbl(TextBox1.Text)
            TextBox1.Clear()
            Select Case tipo
                Case 1
                    total = num1 / num2
                Case 2
                    total = num1 * num2
                Case 3
                    total = num1 + num2
                Case 4
                    total = num1 - num2
            Case 7
                total = num1 ^ num2
        End Select
            TextBox1.Text = total
    End Sub
    Private Sub RadioButton2_CheckedChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles RadioButton2.CheckedChanged
        Select Case base
            Case 10
                TextBox1.Text = DecToBin(TextBox1.Text)
                base = 2
            Case 8
                total = octToDec(TextBox1.Text)
                TextBox1.Text = DecToBin(total)
                base = 2
            Case 16
                TextBox1.Text = HexToBin(TextBox1.Text)
                base = 2
        End Select
    End Sub
    Private Sub RadioButton4_CheckedChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles RadioButton4.CheckedChanged
        Select Case base
            Case 10
                TextBox1.Text = Oct(TextBox1.Text)
                base = 8
            Case 2
                total = BinToDec(TextBox1.Text)
                TextBox1.Text = Oct(TextBox1.Text)
                base = 8
            Case 16
                totalh = HexToDec(TextBox1.Text)
                TextBox1.Text = Oct(TextBox1.Text)
                base = 8
        End Select
    End Sub
    Private Sub RadioButton3_CheckedChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles RadioButton3.CheckedChanged
        Select Case base
            Case 10
                TextBox1.Text = DecToHex(TextBox1.Text)
                base = 16
            Case 2
                TextBox1.Text = BinToHex(TextBox1.Text)
                base = 16
            Case 8
                total = octToDec(TextBox1.Text)
                TextBox1.Text = DecToHex(TextBox1.Text)
                base = 16
        End Select
    End Sub

    Private Sub RadioButton1_CheckedChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles RadioButton1.CheckedChanged
        Select Case base
            Case 2
                TextBox1.Text = BinToDec(TextBox1.Text)
                base = 10
            Case 8
                TextBox1.Text = octToDec(TextBox1.Text)
                base = 10
            Case 16
                TextBox1.Text = HexToDec(TextBox1.Text)
                base = 10
        End Select

    End Sub
End Class