Aegis is a modern toolkit for implementing geographic information systems that is written from the ground up for .NET. It strives to be low on dependencies and faithful to established standards that work such as WKT, WKB, GeoJSON, Shapefiles and more.

It's extensible so if implement a driver for your data source you can hook in all kinds of things that might not be supported out of the box.

The interface is heavily inspired by the fabulous GDAL toolkit but the implementation is independent. Also, Aegis is in a lot of cases relaxed (it doesn't babysit your data) and in other cases a lot more restricted than GDAL (it doesn't try to do everything).

What it does try to do however is to guide you in the right direction when you're wring GIS related software.