My environment is ASP.NET, with data stored in SQL Server. Is there a way to serve Web Feature Services through C#, or will I need to install a mapping server?
You would need a mapping server as @Ragi mentioned. It just doesn't make sense to reimplement the whole stack.
You could start with Geoserver. According to the OpenGeo site, it has the following features:
- Implements OGC services including Web Map Service (WMS 1.1.1 and 1.3.0), Web Feature Service (WFS 1.0.0 and 1.1.0), WFS-Transactional (WFS-T 1.0.0), and Web Coverage Service (WCS 1.0.0 and 1.1.1) Java J2EE application, works with Jetty, Tomcat, WebLogic, WebSphere, JBoss
- Support for many back-end data formats (ArcSDE, Oracle Spatial, DB2, SQL Server, shapefile, GeoTIFF, MrSID, JPEG2000)
- Multiple output formats (GML, shapefile, KML, GeoJSON, PNG, JPEG, TIFF, SVG, PDF, GeoRSS) plus Google Earth integration
- Fully-featured and intuitive web administration interface with REST API for programmatic control
- Full map styling support with Styled Layer Descriptor (SLD), including text-based and graphical editor User- and role-based security subsystem based on Spring Security
I'm just curious though, does it have to be WFS?