A long time ago, in a different life, I produced a fully functional Intrusion Detection System for web projects developed in C# and/or VB.NET using the .NET Framework. The project was called .NETIDS and was a port of PHPIDS. It feature(s/d) individual page scanning, loading as a web module (callback via reflection to specified code in web.config) and the unfeasibly resource-intensive output scanning. Time constraints from my academic life becoming more prevalent led, as is so often the case, to development on the project stalling. This was also partly the case because my primary interest in the web world has moved towards Python and other non-proprietary languages.
That said, I had a heartening email from an initial developer/tester of the project expressing an interest in kickstarting a new development drive. Albert Rajendran has now setup a new GitHub centre for .NETIDS. He's looking for developers! If the idea appeals, have a look through the code, which is pretty well-documented and get in touch. I hope that the development can continue, even though it will be less hands-on in my case. I'm willing to offer advice/ideas for advancing the project at all times, however.