As good as ArcGIS is, you don't need to use it. A lot of the MVC3 crowd (Myself included) are using the following 3 Open source projects off Codeplex these days:
Dot Spatial : http://dotspatial.codeplex.com/
Sharp Map : http://sharpmap.codeplex.com/
Bru Tile : http://brutile.codeplex.com/
all three of them are capable of interfacing to everything from humble shape files right through to massive PostGIS databases as well as all the latest MS-SQL 2008 versions with spatial support.
The code behind most of these projects is our good old friends Gdal, Proj4 and the many other things that sit behind 90% of the GIS software on the planet.
Add to that the likes of Quantum GIS ( My Desktop GIS of choice) : http://www.qgis.org/
and you also have a fantastic tool to preview and manipulate your data.
Getting the data in/out of your projects database and performing general ETL and transforming queries on it ready for your projects to use is where the final bit of the puzzle comes in - Geo Kettle : http://www.spatialytics.org/projects/geokettle/
and you have a full suite for any GIS developer on the .NET platform...