Using Automation in C# is a pain, primarily because C# doesn't support
Optional parameters, and unfortunately MS usually just tagged on extra
parameters as Optional whenever they updated the automation interfaces.

This is why in VB6 you can late-bind an Excel object and the same method for
accessing the contents of a cell will work regardless of the version of
Excel.

There are reams of articles concerning Office Development with Visual
Studio:

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnoxpta/html/vs
officedev.asp

but very little about using Visual Studio.NET.

Anyway, I digress. An article you might find of use is:

Binding for Office automation servers with Visual C# .NET
http://support.microsoft.com/default.aspx?scid=kb;en-us;302902

You might want to look at this too:

Applied Remoting
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnadvnet/html/v
bnet05272003.asp

Another solution that we have used ourselves is to write an Automation
wrapper in VB6 as an COM DLL that late-binds Excel and then reference it
from your C#.NET project. You have to do a big of jiggery-pokery to get the
COM component to expose it's interface so that C#.NET can use it, but apart
from that it works. Can't vouch for decent performance though since there's
lots of calls to IDispatch and other interfaces.

Regards...Andrew

P.S. Don't forget to modify the DCOM Config for the Microsoft Excel
Application.