The SixPack rapid development library is a collection of classes for rapid development on the .NET/Mono platform. It has been built with medium to large scale sites in mind, and supports high performance requirements (thousands of concurrent users per server.)
SharpPcap is a packet capture framework for the
.NET environment, based on the famous pcap/WinPcap
libraries. It provides an API for capturing,
injecting, analyzing, and building packets using
any .NET language such as C# and VB.NET.