In order to define a method in C that is callable by Lua it has to match a given signature and use the Lua API to retrieve parameters and return results. I\'m writing a C# wrapp
You could expose your C# as COM, which would allow all the (public) methods to be called be external apps.
Or, expose a single C# function which would call the appropriate other function, perhaps hard-coded for the list of actual functions in C#, or perhaps using reflection. It might take an arbitrary sized array for the parameters.