This page contains reference documentation for the DisplayVertexNormals member. This member sets or gets whether or not the mesh renders vertex normals.
int DisplayVertexNormals;
Examples are as follows:
ParametricMesh editMesh = new ParametricMesh; editMesh.DisplayVertexNormals = 1; editMesh.DisplayVertexNormals = !editMesh.DisplayVertexNormals;
For sample code: