title: Converting from one nullable type to another nullable type
body: <p>How can one convert from a nullable instance of class A to nullable instance of class B, while B is subclass of A, I tried this but it crashes:</p>
  
  <pre><code>class A
  {
  }
  
  class B:A
  {
  }
  
  A? instance_1=something_maybe_null;
  
  if (instance_1.GetType() == typeof(B))
  {
      ((B)(instance_1))?.some_method_in_B(paramters);
  }
  </code></pre>
  
  <p>And if I move ? into parathesis, it doesn't compile:</p>
  
  <pre><code>...
  if (instance_1.GetType() == typeof(B))
  {
      ((B)(instance_1)?).some_method_in_B(paramters);
  }
  </code></pre>