I know this post is old, but in case anyone is still looking…
CoordinateSharp is available as a Nuget package. It’s a standalone packge that can handle sun as well as moon times.
Celestial cel = Celestial.CalculateCelestialTimes(85.57682, -70.75678, new DateTime(2017,8,21));
Console.WriteLine(cel.SunRise.Value.ToString());
Note:
It assumes DateTimes are always in UTC.
Lastly, you may need to reference the Celestial objects Sun/Moon .Condition if a date returns null. This occurs when the sun is up/down all day.
EDIT 1/9/2019
The library has changed dramatically since this post. It can now handle local times as well.