Using Outlook COM add-in with C#

Hi, I'm trying to use C# to create an application that uses Outllok features. I have added the "Microsoft Outlook 11.0 Object library" as a reference to my Visual Studio project but when I try to create the Outlook application with the following line: Outlook.Application oApp; I get the following error "The type or namespace name 'Outlook' could not be found (are you missing a using directive or an assemble reference?)" Does anyone know what using line I should add? I've tried: using Microsoft.Office.Interop.Outlook; using Outlook; thanks in advance, Leo