Export stl files with C# component in GH

[piac (Giulio Piacentino)]

The method @dsonntag mentions will work nicely for all supported file extensions.
Otherwise, if you want to export meshes to OBJ in Rhino 6, you can use:
https://developer.rhino3d.com/api/RhinoCommon/html/M_Rhino_FileIO_FileObj_Write.htm

See this thread for an example:

How to write selected Mesh to an .obj file?

Hi Rolf, as far as i understand, only a few plugins support access (using COM and IDispatch) through the plugin object, eg RhinoScript or Grasshopper. The “OBJ Export” plugin does not support it i guess. But even if it would support access, i don’t think you could export unbaked GH geometry as OBJ with it, as it was made to export geometry placed in the document. For this, in V5, you could just script the _Export command. The new FileObj class in the Wip does appear to be the thing to use but …

Finally, writing a simple version of an STL file is not terribly complicated. I wrote Turtle a while ago, and it contains an example:

piac/TurtleMesh/blob/master/Turtle/Serialization/Persistance.cs

also the second link above contains a definition that already does that. Check it out!