要更新Angular SideNav中的内容，需要通过Angular路由守卫进行操作。以下是解决该问题的代码示例：

在ngOnInit中注册路由守卫：

export class MyComponent implements OnInit, OnDestroy {
  private routerEventsSubscription!: Subscription;

  constructor(private router: Router) {}

  ngOnInit() {
    this.routerEventsSubscription = this.router.events.subscribe(event => {
      if (event instanceof NavigationStart) {
        // Update SideNav content
      }          
    });
  }

  ngOnDestroy() {
    this.routerEventsSubscription.unsubscribe();
  }
}

在路由守卫中更新SideNav内容：

export class MyComponent implements OnInit, OnDestroy {
  ...

  ngOnInit() {
    ...

    this.routerEventsSubscription = this.router.events.subscribe(event => {
      if (event instanceof NavigationStart) {
        const route = this.router.config.find(r => r.path === this.router.url);
        // Update SideNav content based on the current route
      }          
    });
  }

  ...
}