I've added a reference to Microsoft.Office.Interop.Excel and added some code for Excel automation.

But when I run it, I get:

Retrieving the COM class factory for component with CLSID {00024500-0000-0000-C000-000000000046} failed due to the following error: 80040154 Class not registered (Exception from HRESULT: 0x80040154 (REGDB_E_CLASSNOTREG)).

I couldn't find anything called Microsoft Excel something in the COM section of the Add Reference dialog.

What do I need (to do) ?

Also, I'm running this in a web app - will that cause me any problems? The examples I've seen all run in Forms.