Don't use ArrayList and HashTable. They are outdated. Use List and Dictionary instead:
Dim x As New List(Of String) From {"a", "b"}
Dim y As New Dictionary(Of String, Integer) From {{"C", 3}, {"D", 8}}
For Each item As String In x
MessageBox.Show(item)
Next
For Each key As String In y.Keys
MessageBox.Show(key + ", " + y(key).ToString())
Next
There are many ways to "navigate" those collection types, but that's one way.