I am sharing my C# code for Netduino 2 here. The project uses Ultrasonic distance sensor (HC-SR04) with 8x8 LED matrix (available in Adafruit store http://www.adafruit.com/products/872 ). When the object is close the whole LED matrix is ON, when the object moves far away the number of LEDs which are ON reduces. It also generates sound based on the proximity of the object.
I will be writing cleaner library with classes etc later. Any suggestion to improve the efficiency of the code is welcome.