This is already an old post but with MapWinGIS v4.9.2 you can use
Shape.ClosestPoints (http://www.mapwindow.org/documentation/mapwingis4.9/class_shape.html#a50fb5435d697e3e59d31131d9e65c5e0)
or Shapefile.GetClosestVertex (http://www.mapwindow.org/documentation/mapwingis4.9/group__shapefile__selection.html#ga43e6c5f88c8a0b1a01239b02acc8fa77)
Thanks,
Paul
Shape.ClosestPoints (http://www.mapwindow.org/documentation/mapwingis4.9/class_shape.html#a50fb5435d697e3e59d31131d9e65c5e0)
or Shapefile.GetClosestVertex (http://www.mapwindow.org/documentation/mapwingis4.9/group__shapefile__selection.html#ga43e6c5f88c8a0b1a01239b02acc8fa77)
Thanks,
Paul