Here is a nifty class to handle an angle. it will wrap around increments and decrements that exceed 360 or 0, e.g. adding 20 to 350 will give 10 not 370 and subtracting 10 from 5 will give 355 not -5.
Code sample:
Angle angle = 0;
double angle2 = angle + 5;
Console.WriteLine("a1:{0) a2:{1}",angle,angle2);
//Output: a1:0 a2:5