Check if all leaf nodes are at same level in vb.net

Vb program for Check if all leaf nodes are at same level. Here problem description and explanation.

' Include namespace system
Imports System 
'  Vb.net program for
'  Check if all leaves are at same level 

'  Binary Tree Node
Public Class TreeNode 
    Public  data As Integer
    Public  left As TreeNode
    Public  right As TreeNode
    
    Public Sub New(ByVal data As Integer)
        '  Set node value
        Me.data = data
        Me.left = Nothing
        Me.right = Nothing
    End Sub

End Class
public Class BinaryTree 
    Public  root As TreeNode
    Public  depth As Integer
    
    Public Sub New()
        
        '  Set initial tree root
        Me.root = Nothing
        Me.depth = -1
    
    End Sub
    
    Public Sub checkLeafHeight(ByVal node As TreeNode, 
                               ByVal level As Integer)
        if (node IsNot Nothing) Then 
            '  Test node is leaf or not
            if (node.left  Is  Nothing AndAlso
		 node.right  Is  Nothing) Then 
                if (Me.depth = -1) Then 
                    '  This is first leaf node
                    '  Get node level
                    Me.depth = level
                ElseIf (Me.depth <> level) Then 
                    '  When two leaf nodes is different level
                    Me.depth = -2
                    Return
                End If

            End If

            if (Me.depth <> -2) Then 
                '  Recursively visit left and right subtree
                Me.checkLeafHeight(node.left, level + 1)
                Me.checkLeafHeight(node.right, level + 1)
            End If

        End If

    
    End Sub
    
    Public Sub isSameLevelLeaf()
        Me.depth = -1
        '  Test
        Me.checkLeafHeight(Me.root, 1)
        '  Display result
        if (Me.depth < 0) Then 
            '  Two possible case
            '  1) When tree empty
            '  2) When leaf node are not same level
            Console.WriteLine("No")
        Else 
            '  When leaf node is same level
            Console.WriteLine("Yes")
        End IF

    
    End Sub
    
    Public Shared Sub Main(ByVal args As String())
        '  Create new tree
        Dim tree As BinaryTree = New BinaryTree()
        '    Make A Binary Tree
        '    --------------------
        '      1
        '     /  \
        '    2    3
        '   /    /  \
        '  4    5    6
        ' insertion of binary Tree nodes
        tree.root = New TreeNode(1)
        tree.root.left = New TreeNode(2)
        tree.root.right = New TreeNode(3)
        tree.root.right.right = New TreeNode(6)
        tree.root.right.left = New TreeNode(5)
        tree.root.left.left = New TreeNode(4)
        tree.isSameLevelLeaf()
        '  Add new node
        tree.root.left.left.left = New TreeNode(7)
        '   When add new node
        '    -----------------------
        '          1
        '         /  \
        '        2    3
        '       /    /  \
        '      4    5    6
        '     /
        '    7  
        tree.isSameLevelLeaf()
    
    End Sub

End Class

Output

Yes
No