user: Is there a way to configure a PWA with a Service Worker to _not_ display the cached version of the page when the device is online?

assistant: Yes, you can configure a PWA with a Service Worker so that it does not display the cached version of the page when the device is online. This can be done by setting the "mode" parameter of the Fetch API to "no-cache", which will ensure that the page is always fetched from the server rather than from the cache. Additionally, you can also use the "cacheOnly" option to ensure that the page is only fetched from the cache. This can be useful if you want to ensure that only the most recent version of the page is displayed.

user: Yes, but I want it to work conditionally. How can I make it so that my PWA only loads the cached version while offline, but still loads the most up to date data from my servers when a network connection is available?

assistant: To make your PWA load the cached version while offline and the most up-to-date data from your server when a network connection is available, you can implement a strategy called "Network First, Cache fallback" using the Service Worker.

Here are the general steps to implement this strategy:

1. In your Service Worker, intercept all network requests using the `fetch` event.
2. Check if there is an available network connection.
3. If there is a network connection, make a fetch request to the server and return the response to the browser.
4. If there is no network connection, attempt to retrieve the requested resource from the cache. If the resource is not found in the cache, return a fallback response.
5. If the resource is found in the cache, return the cached response to the browser.

Here's a sample code for implementing the "Network First, Cache fallback" strategy in the Service Worker:

```csharp
self.addEventListener('fetch', event => {
  event.respondWith(
    fetch(event.request)
      .then(response => {
        // Clone the response to store it in the cache
        const clonedResponse = response.clone();
        caches.open('my-cache')
          .then(cache => cache.put(event.request, clonedResponse));
        // Return the response to the browser
        return response;
      })
      .catch(() => {
        // If there's no network connection, try to retrieve the resource from the cache
        return caches.match(event.request)
          .then(cachedResponse => {
            if (cachedResponse) {
              // If the resource is found in the cache, return it to the browser
              return cachedResponse;
            } else {
              // If the resource is not found in the cache, return a fallback response
              return new Response('You are offline.');
            }
          });
      })
  );
});
```

In this code, the `fetch` event is intercepted, and a `fetch` request is made to the server. If the `fetch` request succeeds, the response is stored in the cache, and the response is returned to the browser. If the `fetch` request fails (i.e., there is no network connection), the Service Worker attempts to retrieve the resource from the cache. If the resource is found in the cache, it is returned to the browser. If the resource is not found in the cache, a fallback response is returned to the browser.

This way, when the device is offline, the PWA will load the cached version of the content, and when the device is online, the PWA will load the most up-to-date data from the server.