How do I return a view from Web API action?

You can return one or the other, not both. Frankly, a WebAPI controller returns nothing but data, never a view page. A MVC controller returns view pages. Yes, your MVC code can be a consumer of a WebAPI, but not the other way around.

For More Information Please Refer: https://www.codeproject.com/Questions/1016736/How-to-return-MVC-View-from-web-API