Imports System
Imports System.Text
Public Module Module1
Public Sub Main()
Dim s as String = "abcdef"
Dim sb As StringBuilder = new StringBuilder()
Dim characters As char() = s.ToCharArray()
For i As Integer = 0 To characters.Length - 1
if i Mod 2 = 0 Then
if (i + 1) < characters.Length Then
sb.Append(characters(i + 1))
End If
sb.Append(characters(i))
End If
Next
s = sb.ToString()
Console.WriteLine(s)
End Sub
End Module
' Run
' badcfe