How to use GDI with given impx-file in my own AddIn

I would like to use the GDI without user interface within my own C# .net AddIn.

I have saved settings for different WFS imports in an impx file for each import. Within my own AddIn, I have an user interface, that result in an selected impx file. After that I want to use the GDI with the selected impx file. I know of the KeyIn "gdi import file=g:\import1.impx", but would like to use the gdi class instead of if possible.

Someone who knows how to do this?