I'm not a .NET developer myself, but I found a couple resources that might help:

- [proj.4][1] is probably the best projections library around; there's a .NET wrapper that seems to be maintained quite regularly [here][2]

- there's another library, called [Proj.NET][3], but the latest build is more than two years old. It's supposed to support Lambert Conic Conformal projections.

- you could implement the projection yourself - i usually use either [the EPSG guidance note on coordinate conversions][4] which uses formulae that can be easily converted to code, and contains examples that can be used to test the conversion; or Snyder's 1987 book [Map projections; a working manual][5], but that one is a bit more mathematical.


  [1]: http://trac.osgeo.org/proj/
  [2]: http://ftp.dfg.ca.gov/Public/BDB/Tools/proj4/
  [3]: http://projnet.codeplex.com/
  [4]: http://www.epsg.org/guides/docs/G7-2.pdf
  [5]: http://pubs.er.usgs.gov/usgspubs/pp/pp1395