NET5.0 Blazor WASM CORS client exception

[tomschrot]

I have a Blazor WASM app and a Web Api to get called by Blzor via HttpClient. Both programs run on the same machine (and also in production environment which should not be to exotic for a small business application!).

Calling the Web Api from the Blazor client result in a client CORS exception

Access to fetch at 'http://localhost:4040/' from origin 'https://localhost:5001' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource. If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled.

which is the expected behavior for this case.

In an former api project I developed in PHP, that had the same client behavior, I can bypass the CORS exception by simply setting the response header.

Please read the whole question on the site:

https://stackoverflow.com/questions/64858434/net5-0-blazor-wasm-cors-client-exception?noredirect=1#comment114676627_64858434

where I also posted the code.

Unfortunately nobody could answer it.