algorithmic modeling for Rhino
any chance this might be easier using Python?
import rhinoscriptsyntax as rs
a = rs.AddHatch(myCrv)
The python version that Daniel posted has to be the easiest/shortest answer, but if you want to use VB.NET I updated the wiki sample to a RhinoCommon version.
Until the next V5 beta or V4 version of Grasshopper, you will need to use a different version of the Hatch.Create function (which takes a list of curves instead of a single curve).