public bool HasNormals {get;}

// <summary>
// This method gets the normal coordinate of a multipatch and does something with it.
// </summary>
// <param name="multipatch">The input multipatch.</param>
// <param name="patchIndex">The index of the patch (part) for which to get the normal.</param>
public void DoSomethingWithNormalCoordinate(Multipatch multipatch, int patchIndex)
{
  if (multipatch.HasNormals)
  {
    // 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.
    }
  }
}