title: i got error "Value cannot be null.\r\nParameter name: serviceType"
body: <p>I was following a tutorial , but after setting the project build path, I run the project and navigate to plugins. Then I got the following error.
  An exception of type 'System.ArgumentNullException' occurred in Autofac.dll but was not handled in user code,</p>
  
  <blockquote>
    <p>"Value cannot be null.\r\nParameter name: serviceType"</p>
  </blockquote>
  
  <p>and i don't know that which method i should add and in which class?</p>
  
  <p>Please help! </p>