title: Check if class being used?
body: <p>Simple problem,
  is it possible to check if a class is being used or not?</p>
  <pre><code>class A { }
  class B { }
  
  class TestClass
  {
      static void Main(string[] args)
      {
          var a = new A();
      }
  }
  </code></pre>
  <p>I want to loop through all classes with reflection and get back that <strong>A is being used</strong> somewhere.
  By &quot;used&quot; I mean there is a reference to it somewhere, it does not need to be loaded necessarily already. In the same way Visual Studio show how many references an object has.</p>