Comments by Moleter (Top 3 by date)

Refer to this article for exporting DataSet into an Excel file in C# and also this code for exporting that excel file in ASP.NET.
I hope this helps, note that those sample codes use this C# library for excel files.

You should probably take a look at this word processing library for C#, more specifically see this demo. That sample demonstrates how you can take a HTML content from some WYSIWYG editor and add it into a document. I presume this is exactly what you're looking for.