Export to .shp (Shape file) from AutoCAD map

To export to a shape file from AutoCAD map, Go to File> export> other GIS formats.
On the next menu, select the tab labeled "data".
   in order not to receive the error "this field name already exists"
select only objects...
hit OK





To export a Civil 3D surface to a raster , go to the Prospector and right-click on the surface and choose 'Export to DEM'. On the bottom of the menu, switch the file type from USGS .dem to GEOTIFF .tif file.

To use a large surface in Civil 3D without too much overheard use Autodesk's Map 'connect data' feature and connect to the GIS shape files of contours or surface elevations in various forms (hilshades form-.adf)
without utilizing too many resources. Make sure to match the CRS (coordinate reference system).

Assign elevations to contours from an esri shape-file

Assigning contour lines from ESRI ArcGIS polylines with object data.

http://www.thecadmasters.com/wordpress/index.php/2011/03/16/assign-elevations-to-contours-from-an-esri-shape-file/

This link describes in very easy steps how to create a query to give elevations to polylines with object data but with an elevation of zero.