Silverlight 5 and VertexBuffer.GetData()

我正在尝试在Silverlight 5中实现3D模型碰撞。为此，我创建了一个边界框（就像在XNA4.0中一样）：

我在此链接中看到了相同的问题VertexBuffer.GetData（）和Silverlight 5，但没有找到答案。

 public BoundingBox GetBoundingBoxFromModel(Model model)
    {            
        BoundingBox boundingBox = new BoundingBox();
            foreach (ModelMeshPart part in model.Meshes[0].MeshParts)
            {
                VertexPositionNormalTexture[] vertices = new VertexPositionNormalTexture[part.NumVertices];
                Vector3[] vertexs = new Vector3[vertices.Length];
                part.VertexBuffer.GetData<VertexPositionNormalTexture>(vertices);                    

                for (int index = 0; index < vertexs.Length; index++)
                {
                    vertexs[index] = vertices[index].Position;
                }
                boundingBox = BoundingBox.CreateMerged(boundingBox, BoundingBox.CreateFromPoints(vertexs));
            }            
        return boundingBox;
    }