title: Cast Dictionary<Key, Value> to IReadOnlyDictionary<Key, IValue>?
body: <p>We can easily do this :</p>
  
  <pre><code>List&lt;Value&gt; list;
  IReadOnlyList&lt;IValue&gt; List =&gt; list;
  </code></pre>
  
  <p>But how can we do the same with IReadOnlyDictionary?</p>
  
  <pre><code>Dictionary&lt;Key, Value&gt; dict;
  IReadOnlyDictionary&lt;Key, IValue&gt; Dict =&gt; dic; //impossible
  </code></pre>