With HTML5 ASP.NET MVC Report Viewer you can have the viewer configured in code. The MVC wrapper renders the widget and links to the required JS, CSS and HTML resources on the page.
The MVC viewer works like the HTML5 Viewer in a client-server pair with the Reporting REST Service.
The MVC wrapper of the HTML5 Viewer can be used in MVC projects, where the MVC project appears as the client for the Reporting REST Service. Even if the Reporting REST Service is added in the same MVC project, the service does not operate in the MVC context. If you need to use data modified in the MVC context, it has to be saved in the data source, from where the Reporting REST service can access it.