title: Is it necessary to check null values with constructor injection?
body: <p>I'm using .NET Core constructor injection.
  In a code review from a colleague, he raised the question if I should check for null values on injected dependencies in controllers.</p>
  
  <p>Since the framework is responsible for creating an instance of the service, it seems to me that it would take care of any errors and never have a null value dependency passed to a constructor. I don't have any factual evidence for this though, so I'd like to know if it's possible that a null check may be necessary.</p>
  
  <p>For example, should I check if 'myService' is null in the following code? (Assuming the code is configured to use DI)</p>
  
  <pre><code>public class MyController
  {
      private readonly IMyService _myService;
  
      public MyController(IMyService myService) 
      {
          _myService = myService;
      }
  }
  </code></pre>