The Accord.NET framework is a.NET machine learning framework that helps in making audio and image processing easy. This one is for the C# programmers.
Microsoft's Computational Network is another library which supports C# language that enhances the modularization and the maintenance of separating computation networks, providing learning algorithms and model descriptionsToolKit.
Have a look at logic engines that work on the .net platform, such as prolog.net or p#. It should be relatively easy to create a c# application that interfaces with one of these. These examples use prolog, so you might be able to take advantage of other work done in prolog by other people.
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