Access Outlook from C#

From within a C# .Net app I want to create a distribution list in Outlook.

According to what I have read on the Microsoft site at http://support.microsoft.com/kb/310244 you need to add a reference to the Microsoft Outlook 10.0 Object Library, which I have done (Outlook 11 not 10) and then you can write ...

Outlook._Application olApp = new Outlook.ApplicationClass();

to get started.

I have put
using Microsoft.Office.Interop.Outlook;

at the top of the class file.

But it says 'The type or namespace Outlook could not be found, are you missing a using directive or assembly reference'

Can anyone tell me what I am missing or what reference I need to add. Thanks very much.