Subtraction of alternate nodes of linked list in vb.net

Vb program for Subtraction of alternate nodes of linked list. Here problem description and other solutions.

' Include namespace system
Imports System 
'    Vb.net program for
'    Subtraction of the alternate nodes of linked list

'  Linked list node
Public Class LinkNode
    Public  data As Integer
    Public  [next] As LinkNode
    Public Sub New(ByVal data As Integer)
        Me.data = data
        Me.next = Nothing
    End Sub
End Class

public Class SingleLL
    Public  head As LinkNode
    Public  tail As LinkNode
    Public Sub New()
        '  Set initial value
        Me.head = Nothing
        Me.tail = Nothing
    End Sub
    Public Sub insert(ByVal data As Integer)
        Dim node As LinkNode = New LinkNode(data)
        if (Me.head  Is  Nothing) Then
            '  Add first node
            Me.head = node
        Else
            '  Add node at the end position
            Me.tail.[next] = node
        End IF
        '  New last node
        Me.tail = node
    End Sub
    '  Display linked list element
    Public Sub display()
        if (Me.head  Is  Nothing) Then
            Return
        End If
        Dim temp As LinkNode = Me.head
        '  iterating linked list elements
        while (temp IsNot Nothing)
            Console.Write(" " + temp.data.ToString() + " →")
            '  Visit to next node
            temp = temp.[next]
        End While
        Console.WriteLine(" NULL")
    End Sub
    '  Find the subtraction of all alternate 
    '  nodes in linked list
    Public Sub alternateSubtraction()
        '  Define resultant variables
        Dim result As Integer = 0
        Dim counter As Integer = 0
        '  Start to first node of linked list
        Dim temp As LinkNode = Me.head
        '  iterating linked list elements
        while (temp IsNot Nothing)
            if (counter Mod 2 = 0) Then
                '  When get alternate node
                if (result = 0) Then
                    result = temp.data
                Else
                    result = result - temp.data
                End IF
            End If
            '  Node counter
            counter += 1
            '  Visit to next node
            temp = temp.[next]
        End While
        Console.WriteLine(" Alternate nodes subtraction : " + 
                          result.ToString())
    End Sub
    Public Shared Sub Main(ByVal args As String())
        Dim sll As SingleLL = New SingleLL()
        '  Add node in linked list
        '  4 → 7 → 2 → 9 → 1 → 3 → 4 → 3 → 6 → NULL
        sll.insert(4)
        sll.insert(7)
        sll.insert(2)
        sll.insert(9)
        sll.insert(1)
        sll.insert(3)
        sll.insert(4)
        sll.insert(3)
        sll.insert(6)
        '  Display of linked list nodes
        sll.display()
        '  Test
        sll.alternateSubtraction()
    End Sub
End Class

Output

 4 → 7 → 2 → 9 → 1 → 3 → 4 → 3 → 6 → NULL
 Alternate nodes subtraction : -9