IEnumerable<T> conversion
<p>just a newbie question. Got this:</p>

<pre><code>
class Base&lt;T&gt; {/*...*/}
class Der&lt;T>: Base&lt;T> {/*...*/}

interface Sth&lt;T>{
  IEnumerable&lt;Base&lt;T>> Foo {get;}
}

// and implementation...
class Impl&lt;T>: Sth&lt;T> {
  public IEnumerable&lt;Base&lt;T>> Foo {
    get {
      return new List&lt;Der&lt;T>>();
    }
  }
}
</code></pre>

<p>the question is: how to make it work/compile? The error is, obviously, not implicit convertion found from List&lt;Der&lt;T>> to List&lt;Base&lt;T>>. If I cast it explicitly InvalidCastException occurs.</p>

<p>Any help needed :)</p>
