Unique permutation in c# gives no dup but vb.net does - vb.net

Question

So I am converting an extension method to find permutations of a generic list from c# to vb
The code in c# does not return duplicate. For example: {1,2} is same as {2,1} and {1,1} is not allowed. The vb code that I convert, however gives me a duplicate. Can someone help me spot the problem. I got the c# code from accepted answer in this thread: How to Generate Combinations of Elements of a List<T> in .NET 4.0
Here is the vb code:
Module HelperPermutation
<Extension()>
Public Function Combinations(Of T)(elements As IEnumerable(Of T), k As Integer) As IEnumerable(Of T())
Dim result As List(Of T()) = New List(Of T())
If (k = 0) Then
result.Add(New T(-1) {})
Else
Dim current As Integer = 1
For Each element In elements
result.AddRange(elements _
.Skip(current = current + 1) _
.Combinations(k - 1) _
.Select(Function(c) (New T() {element}).Concat(c).ToArray())
)
Next
End If
Return result
End Function
End module
I tried to add Distinct but it still gives me duplicates.
And this is my console app to use that extension method:
Dim list As New List(Of Integer) From {1, 2, 3}
Dim array = list.Combinations(2)
Console.WriteLine("# of permutation: " & array.Count)
For Each value In array
Console.WriteLine("-------Pairs: " & value.Count)
For i As Integer = 0 To value.Count - 1 Step 1
Console.WriteLine("value = " & value.ElementAt(i))
Next
Next
Console.ReadLine()

Answer 1

current = current + 1 is not doing assignment. It's an equality test, so the result of that expression is boolean. Since there is no overload for Skip() that takes a boolean, it seems like you might not be using Option Strict. I would highly suggest using it for spotting mistakes like this.
There is no post-increment built into the VB language, but luckily, you can create your own.
Function PostIncrement(ByRef arg As Integer) As Integer
arg += 1
Return arg - 1
End Function