Conversion from binary to octal in vb.net

Vb program for Conversion from binary to octal. Here mentioned other language solution.

' Include namespace system
Imports System 
'  Vb.net program for
'  Convert Binary number into Octal number
public Class Convert
    ' Convert decimal number into octal
    Public Function  octal(ByVal number As Integer) As Integer
        Dim result As Integer = 0
        Dim multiplier As Integer = 1
        Dim remainder As Integer = 0
        while (number <> 0)
            remainder = number Mod 8
            result = (remainder * multiplier) + result
            multiplier *= 10
            number = (number / 8)
        End While
        Return  result
    End Function
    Public Sub binaryToOctal(ByVal num As String)
        if (num.Length = 0) Then
            ' When empty binary number
            Return
        End If
        ' Some useful variable
        Dim flag As Boolean = False
        Dim decimalNo As Integer = 0
        Dim counter As Integer = 0
        Dim index As Integer = num.Length - 1
        ' We Assume that given binary number is valid
        ' Here - indicates negative binary number
        ' First convert binary to decimal
        ' Example = 10111 => 23
        while (index >= 0)
            if (num(index) = "1"c) Then
                decimalNo += (1 << counter)
            ElseIf (num(index) <> "0"c) Then
                    if (index = 0 AndAlso num(index) = "-"c) Then
                        ' When get negative number
                        flag = True
                    Else
                        ' Not a valid binary number
                        Return
                    End IF
                End If
            counter += 1
            index -= 1
        End While
        ' When given number is 
        Dim output As Integer = Me.octal(decimalNo)
        if (flag = True) Then
            output = -output
        End If
        ' Display given number
        Console.Write("Binary : " + num)
        ' Display result
        Console.WriteLine(" Octal : " + output.ToString())
    End Sub
    Public Shared Sub Main(ByVal args As String())
        Dim task As Convert = New Convert()
        ' Test Case
        task.binaryToOctal("1111")
        task.binaryToOctal("10111")
        task.binaryToOctal("101011")
        task.binaryToOctal("11011")
        task.binaryToOctal("-1000110")
    End Sub
End Class

Output

Binary : 1111 Octal : 27
Binary : 10111 Octal : 37
Binary : 101011 Octal : 153
Binary : 11011 Octal : 33
Binary : -1000110 Octal : -116