title: Register an instance of a service in Prism.Unity which relies on another service
body: <p>I have an authentification service, that I register in my Unity Container like so:</p>
  
  <pre><code>Container.RegisterInstance&lt;IAuthenticationService&gt;(new AuthenticationService());
  </code></pre>
  
  <p>My problem is that my <code>AuthentificationService</code> relies on <code>INavigationService</code>, and its constructor takes this as an argument:</p>
  
  <pre><code>public AuthenticationService(INavigationService navigationService)
  </code></pre>
  
  <p>From my understanding, the Unity Container is responsible for injecting the <code>INavigationService</code> implementation. But in this case, I am providing the <code>AuthenticationService</code> instance, so how can I tell Unity to inject the <code>INavigationService</code> in my <code>AuthentificationService implementation</code>?</p>