I have been asked to build an MVC 4 project where the controller method can be invoked by an external service. 

I have very limited information regarding this external service except that each service endpoint will render a different view. 

My job is to create these views and have the controller be invoked manually to render the view the service endpoint asks for. 

The service and the MVC project will be built as separate projects. The MVC project is a standalone project. The service expects the HTML of the form back, which it would pass on to another project.

I don't know a way to invoke controller through code-behind from a project that lives in a different solution. Any link/tutorial would be great.

Apologies, if my question seems vague or lack information. Please let me know if it does, and I'd add more information.