When consuming an Api App from c# the Azure App Service SDK helps us generate Client Code to improve the develoment process. (read more here)
When testing the generated code you might get an error of ‘Method Not Allowed’ and status code 405 even if the security settings is correct and the API app works perfectly when trying to use it via Logic App, Postman/fiddler/swagger etc.
If the thrown exception looks something like this:
Then the problem probably is an incorrect generated URI from the code generator where it has used http instead of https. (common in several places with API Apps always should be https)
To check this go in to the class of the ServiceClient ( in my case FlatFileEncoder ) and check the base URI settings, as you can see on the image bellow mine where generated with http instead of https.
Changing the URI from http to https and it starts working, my code is executed and the result from the FlatFileToXML function is returned as expected.