On the Web API Samples page for Web API Conditional Operations Sample, the documentation correctly formats the wildcard form of the If-None-Match header as:
However, over on the Perform operations using the Web API page about the same, Perform conditional operations using the Web API, the documentation errantly puts the asterisk in double quotes:
With the asterisk in double quotes, the Web API returns a 400 Bad Request status code with error message:
400 Bad Request
The specified If-None-Match condition isn't supported for a PATCH request.
(aside: the two spaces between "isn't" and "supported" are not a typo)
Please correct the documentation.
This will be fixed in the docs. The change is pushed to the master repo and will go live by Tuesday (Given that it is the long Labor Day weekend).
BTW - For doc issues, best results are achieved by using the GitHub issues reporting on the current docs rather than the archieved ones.
In this case: https://docs.microsoft.com/en-us/powerapps/developer/common-data-service/webapi/perform-conditional-... rather than the old: https://docs.microsoft.com/en-us/previous-versions/dynamicscrm-2016/developers-guide/mt607711(v=crm....)