how to enable mix mode for asp.net web forms app

Hi,

I have a .net framework 2.0 dll for AX 4.0 business connector that I need it working in new .net 4.7.1 Web API project.

I tried but it is not working , it throw error said the application is in break mode.

but It works well in windows form app same 4.7.1 by add useLegacyV2RuntimeActivationPolicy to app.config

<startup useLegacyV2RuntimeActivationPolicy="true">
<supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.7.1" />
</startup>

I tried to add this to Web API, web.config , but it does not works, how can I make the web API project enable the mix mode like windows form app?

Regards,