Imports Microsoft.Office.Interop
[...]
Dim oApp As Outlook.Application = New Outlook.Application()
Dim oNS As Outlook.NameSpace = oApp.GetNamespace("mapi")
oNS.Logon("Outlook", Missing.Value, False, True) 
Dim cContacts As Outlook.MAPIFolder = oNS.GetDefaultFolder( _
  Outlook.OlDefaultFolders.olFolderContacts)
Dim oItems As Outlook.Items = cContacts.Items
Dim oCt As Outlook.ContactItem
For i As Integer = 1 To oItems.Count - 1
oCt = oItems(i)
Next
[...]