Nand -
There isn't a separate API for .NET for NI-Motion software. You will have to load the motion dll to call the functions that are supplied with the driver, available for download here: http://digital.ni.com/softlib.nsf/websearch/4405A2D094B3D6D386256DE300707983?opendocument&node=132060_US
Here is a document that should get you started. If you have more questions, refer to Microsoft's help on calling functions from a dll.
How to Import a DLL in Visual Studio .NET?
http://digital.ni.com/public.nsf/websearch/FA5837624BE5300B86256CBA00096E8C
Hope this helps.
Regards-
Julie S.
Applications Engineer
National Instruments
