80040154 Class not registered ERROR in Outlook 2010 Add In

Question

I am using Visual Studio 2010 to create a Outlook 2010 Add In. I try to create a new Outlook AppointmentItem to work with thinking that I can add it to the calendar eventually.

Microsoft.Office.Interop.Outlook.AppointmentItem tempApp = new Microsoft.Office.Interop.Outlook.AppointmentItem();

But when the AddIn runs and trys to create the AppointmentItem object, I get this error on the line above.

System.Runtime.InteropServices.COMException was unhandled by user code
      Message=Retrieving the COM class factory for component with CLSID {00061030-0000-0000-C000-000000000046} failed due to the following error: 80040154 Class not registered (Exception from HRESULT: 0x80040154 (REGDB_E_CLASSNOTREG)).
      Source=mscorlib
      ErrorCode=-2147221164

What can I do to "register the class"? I'm guessing it has to do with Microsoft.Office.Interop.Outlook.dll in some way.

Answer 1

The exception message is not very helpful, they could have done a better job with the COM declaration. This is by design, the class is not registered. You must create an instance of it with the Application.CreateItem() method.