Sep 21, 2016 02:59 AM|Yohann Lu|LINK
config.EnableCors(new EnableCorsAttribute("domainname.com", "*", "*"));
The above code will enable CORS for all Web API controllers in your application.
You can refer the following detailed tutorial.
Enabling Cross-Origin Requests in ASP.NET Web API 2:
Please make a test on your side (you can try methods which provided in the tutorial), Then, if you have any error in your code, you could also share us more relevant message to help us reproduce the problem.