public bool HasNormals {get;}

{
  if (multipatch.HasNormals)
  {
    int patchIndex = 0;
    // If the multipatch has normals, then the number of normals is equal to the number of points.
    int numNormals = multipatch.GetPatchPointCount(patchIndex);

    for (int pointIndex = 0; pointIndex < numNormals; pointIndex++)
    {
      Coordinate3D normal = multipatch.GetPatchNormal(patchIndex, pointIndex);

      // Do something with the normal coordinate.
    }
  }
}