title: Impossible to use ref and out for first ("this") parameter in Extension methods?
body: <p>Why is it forbidden to call <code>Extension Method</code> with <code>ref</code> modifier?</p>
  
  <p>This one is possible:</p>
  
  <pre><code>public static void Change(ref TestClass testClass, TestClass testClass2)
  {
      testClass = testClass2;
  }
  </code></pre>
  
  <p>And this one not:</p>
  
  <pre><code>public static void ChangeWithExtensionMethod(this ref TestClass testClass, TestClass testClass2)
  {
      testClass = testClass2;
  }
  </code></pre>
  
  <p>But why?</p>