With Civil 3D 2013 comes some changes in the API. Many of the various items have been combined to streamline the API. This also will create some headaches in doing some additional work to upgrade.
The first thing you may want to do (probably have to do) is to upgrade to Visual Studio 2010. You can use the free or pay version.
Next double click properties and open up the Application tab. Change the Target framework to “.NET Framework 4”. It will make you restart the project, so press the yes button.
Next we need to change the references from 2012 to 2013.
You can change the reference in vb.NET from the properties or in c# in the Solution Explorer. For the AeccXLandLib and the AeccXUiLandLib you want to not use them any more. You will want to use the preassembled Civil 3D version which may be found in:
C:\Program Files\Autodesk\AutoCAD Civil 3D 2013
For 2013 you will also need to add accoremgd.dll as a reference.
For 2013 you will need to change PointEntity to CogoPoint.
Next you will need to replace all of the instances of Autodesk.Civil.Land, Autodesk.Civil.Pipe and the similar typed names. Remove the Land and Pipe liked parts and it should work as long as you aren’t using some of the methods that have changed. If there is you will have to figure out how to change them.