XSBDotNet is a .NETwrapper for the XSB Prolog Engine. It supports both the single-threaded and multithreaded engines and provides object-oriented classes for a complete .NET experience.
The C# XMP Toolkit is a wrapper for Adobe's XMP Toolkit and will allow you to add, modify and/or delete XMP using any .NET 2.0 Application (ie. C#, VB.NET, etc.).