title: Why use ICollection and not IEnumerable or List<T> on many-many/one-many relationships?
body: <p>I see this a lot in tutorials, with navigation properties as <code>ICollection&lt;T&gt;</code>.</p>
  
  <p>Is this a mandatory requirement for Entity Framework? Can I use <code>IEnumerable</code>?</p>
  
  <p>What's the main purpose of using <code>ICollection</code> instead of <code>IEnumerable</code> or even <code>List&lt;T&gt;</code>?</p>