检测是否基于纬度/经度的多边形点

I'd like to detect, on the server side using C# only, whether a Latitude/Longitude based coordinate is within an area (polygon) made up of Latitude/Longitude based points. I believe the right way to do this is raycasting, but maybe there is already a C# implementation out there as it's not trivial?I'd like to detect, on the server side using C#