Mads Torgersen and many other members of the C# team labored tirelessly to assemble the unified C# 3.0 Specification. This document combines the 1.1 version of the spec, the 2.0 version, and various other bits and pieces into one large document some 500 pages in length. Here you will find the definitive technical description of the C# language in the words of the engineers who created it. It is the single most authoritative reference for the C# language. Though not called out by name in this document, many of the people who created the C# language contributed to it, and they are its primary authors.
You can download it directly, or visit the C# language page where you can find a link to it and various related documents.