title: How to pass a parameter to DbContext constructor using Dependency Injection
body: <p>I'm in the middle of reworking my DbContext to support Multitenancy by requiring a tenantId:</p>
  
  <pre><code>public AppContext(int tenantId)            
      {
          _tenantId = tenantId;
      }
  </code></pre>
  
  <p>Before, there was no parameter.</p>
  
  <p>In my service classes, I have the context instantiated with DI: </p>
  
  <pre><code>    private readonly AppContext db;
      private CommService _commService;
  
      public AdminService(AppContext db, CommService commService)
      {
          this.db = db;
          _commService = commService;
      }
  </code></pre>
  
  <p>And in my Controllers, the same thing:</p>
  
  <pre><code>    private readonly CommService _commService;
      public AdminController(CommService commService) {
           _commService = commService;
      }
  </code></pre>
  
  <p>I'm using Unity, but haven't really done much configuration at all - it all just works.</p>
  
  <p>I'll be retrieving the <code>tenantId</code> from my Controllers.  How do I go about passing the tenantId from Controller > Service layer > Constructor?</p>