With enough time, most certainly. You will probably run into problems when your Arduino C/C++ project uses AVR-specific hacks and options like timers and interrupts. From my understanding you can do these more advanced things on the Netduino but there is a significantly different way you'll have to go about coding it.
In order to effectively port the code you'll need a good understanding of C, a strong understanding of C#, as well as the Arduino and Netduino build process, coding conventions, APIs, etc.