static VertexStore GetFreeVxs() { if (s_vxsPool == null) { s_vxsPool = new Stack <VertexStore>(); } if (s_vxsPool.Count > 0) { return(s_vxsPool.Pop()); } else { VertexStore vxs = new VertexStore(); VertexStore.SetSharedState(vxs, true); return(vxs); } }