Private Sub FindMySpecificString(ByVal searchString As String)
   ' Ensure we have a proper string to search for.
   If searchString <> String.Empty Then
      ' Find the item in the list and store the index to the item.
      Dim index As Integer = listBox1.FindStringExact(searchString)
      ' Determine if a valid index is returned. Select the item if it is valid.
      If index <> ListBox.NoMatches Then
         listBox1.SetSelected(index, True)
      Else
         MessageBox.Show("The search string did not find any items in the ListBox that exactly match the specified search string")
      End If
   End If
End Sub

Private Sub FindAllOfMyExactStrings(ByVal searchString As String)
   ' Set the SelectionMode property of the ListBox to select multiple items.
   ListBox1.SelectionMode = SelectionMode.MultiExtended

   ' Set our intial index variable to -1.
   Dim x As Integer = -1
   ' If the search string is empty exit.
   If searchString.Length <> 0 Then
      ' Loop through and find each item that matches the search string.
      Do
         ' Retrieve the item based on the previous index found. Starts with -1 which searches start.
         x = ListBox1.FindStringExact(searchString, x)
         ' If no item is found that matches exit.
         If x <> -1 Then
            ' Since the FindStringExact loops infinitely, determine if we found first item again and exit.
            If ListBox1.SelectedIndices.Count > 0 Then
               If x = ListBox1.SelectedIndices(0) Then
                  Return
               End If
            End If
            ' Select the item in the ListBox once it is found.
            ListBox1.SetSelected(x, True)
         End If
      Loop While x <> -1
   End If
End Sub