.net 新增Area的步骤

            app.UseMvc(routes =>
            {
                routes.MapAreaRoute(
                    name: "PreviewFile",
                    areaName: "PreviewFile",
                    template: "PreviewFile/{controller=Home}/{action=Index}"
                    );
                routes.MapRoute("default", "{controller=Home}/{action=Index}/{id?}");
            });

            app.UseMvc();