C#/.NET scripting library

Please check CS Scripting library

Here is an article about scripting Photoshop CS with C#

This one discusses using LUA as scripting lib with C#.

IronPython is a dynamic .NET scripting language.

IronPython is an implementation of the Python programming language running under .NET and Silverlight. It supports an interactive console with fully dynamic compilation. It's well integrated with the rest of the .NET Framework and makes all .NET libraries easily available to Python programmers, while maintaining compatibility with the Python language.

See IronPython embedding for examples showing ways to call IronPython from .NET apps. The IronPython Calculator and the Evaluator goes into the details of using IronPython from a C# application.