"Nice Angles" - Code Eval challenge
At the heart of the solution, there should be a function that converts decimal degrees into a d°mm'ss" string.  Assuming that the input is in a reasonable domain (between 0 and 360, for example), the conversion algorithm should be simple and regular.  Above all, it should be purely mathematical at this point — you shouldn't be trying to do any string parsing.

Your format string had lots of unnecessary concatenation.

public static string ToDegMinSec(double dec)
{
    int degrees = (int)dec;
    dec = 60 * (dec - degrees);
    int minutes = (int)dec;
    dec = 60 * (dec - minutes);
    int seconds = (int)dec;
    return string.Format("{0}.{1:00}'{2:00}\"", degrees, minutes, seconds);
}