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I have a Blazor WASM application using .Net Core 6, and all of the latest nuget packages, hosted using Azure App Services.

As per my understanding, the browser caches the application DLLs appending a sha256 hash code to the filename. The browser keeps the DLLs cached until it reads a new sha256 hash value on the blazor.boot.json, at which point it replaces the old DLL in the cache with a new one.

As per my observations, this works most of the time. If I look at my own browser application cache, using the dev tools, I will see the same version the DLL today, tomorrow, and the next day, as long as there hasn't been any deployments. Then, after a deployment, I open the application in my browser, go back to my cache, and without needing to manually clear anything or do anything out of the ordinary, I will see the DLL with an updated sha256 code.

However, every once in a while, this isnt the case. For example, I have a user, that rarely uses the development environment. The version of the application dll has been cached since august (2 months ago). Additionally, the contents of the blazor.boot.json correctly indicate the new version of the dll. But still, the old version, with a different SHA hash, remains in her cache.

I've seen this behavior before. I can't quite put my finger on what the difference is in the application changes that lead to successful automatic cache busting vs when the old cache continues to persist.

The simple solution is to have the user delete the entire blazor-resources group of dll's to force a new download. However, as we expand the footprint of the app to new users, I don't want to have to ask them to clear their application cache as we are deploying new versions of the code.

Given this example, it seems the failure is somewhere between the retrieval of the updated blazor.boot.json and whatever standard javascript runs to retrieve the new DLLs, which I believe is in the service-worker.js.

Any assistance regarding:

  1. An explanation of why this might be happening (so that I can reliably reproduce the issue and have a valid test case after it's been fixed)
  2. What code/configuration I may be able to force the DLL download... not on every refresh of the app, but at least when the SHA hash has changed.

Thanks, Mike

Mike
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    [Does the answer useful to you ?](https://stackoverflow.com/a/61256410/7687666) – Jason Pan Oct 14 '22 at 09:21
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    I am having a very similar issue with my Components project. Blazor.boot.json is correctly updated with a new hash for the main project, but my components dll hash is not updated when I make changes to the components. This happen nearly if not 100% of the time. Performing a 'clean' before entering debug *does* solve the issue but obvs this is not ideal. – Rich Freeman Mar 17 '23 at 07:58

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