I discovered Mono yesterday. I think this would be a great way to develop on my NanoPi Duo.
http://www.mono-project.com/

I installed it and tried all the examples and it worked just fine.
Now, the only thing that has be puzzled is how to use C# to gain access to the I/O pins on the Duo.
Has anyone here had any experience with Mono and GPIO ? Specifically, I would like to learn how to do SPI, I2C and general GPIO settings like inputs and outputs and toggle I/O pins.

Thanks.