Visual Basic .NET strings support the For Each statement, so you can iterate over each individual character as follows:
Dim s As String = "ABCDE"
Dim c As Char
For Each c In s
Console.Write(c & ".") ' => A.B.C.D.E.
However, you should bear in mind that For Each loops on string characters aren't optimized. The following solution, that uses the Chars property, is 2-5 times faster:
Dim i As Integer
For i = 0 To s.Length - 1
Console.Write(s.Chars(i) & ".") ' => A.B.C.D.E.