Dwg

Read/Write DXF/DWG files in C#, VB.NET with CadLib: http://www.woutware.com/cadlib.html. Specific versions for .NET 2.0/3.5/4.0 are available. A silverlight version is available as well.

Reading AutoCAD DWG files in C#, VB.NET in managed .NET code is possible in CAD Import .NET software.

http://www.cadsofttools.com/en/products/cad_import_.net.html