Request failure due to CORS policy

[slaval2000]

Using CefSharp version 99.2.90 , when using WPF Sample Example I'm able to do CROS domain request without errors ,
but when i using same code on my WPF application , I'm getting following error.

Access to fetch at 'https://www.arcgis.com/sharing/rest/portals/self?f=json&culture=en-us' from origin 'https://ServerName' has been blocked by CORS policy: Request header field access-control-allow-headers is not allowed by Access-Control-Allow-Headers in preflight response.

What I'm missing ?

[amaitland]

What example are you referring to exactly? There are multiple.

I'm able to do CROS domain request without errors ,

Are you testing with exactly the same set of urls?