Listar elementos combobox

For Each elem As String In ComboBox.Items

Next

For each array

For Each c As String In New String() {"1", "2", "3", "4"}
                MessageBox.Show(c)
            Next

Mostrar elementos de un nuevo array

For Each c As String In New String() {"1", "2", "3", "4"}
    MessageBox.Show(c)
Next

For each reverse

Dim datatxt() As String = File.ReadAllLines("archivo.txt")

For Each s As String In datatxt.Reverse
Next

Eliminar archivos de un directorio

Imports System.IO
Public Class Form1
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim archivos() As String = Directory.GetFiles("c:\directorio", "*.*") ' sin backslash al final de la ruta del directorio
        For Each f As String In archivos
            File.Delete(f)
        Next
    End Sub
End Class

http://bit.ly/2f3pTKV

Obtener archivos de la carpeta Debug y mostrarlos

Dim files() As String
files = System.IO.Directory.GetFiles(Application.StartupPath, "*.sql")
Dim x As String
For Each x In files
MessageBox.Show(x)
Next

'Las 6 líneas de arriba se pueden reducir a:
For Each x As String In System.IO.Directory.GetFiles(Application.StartupPath, "*.sql")
MessageBox.Show(x)
Next