title: How can I default a parameter to Guid.Empty in C#?
body: <p>I wish to say:</p>
  
  <pre><code>public void Problem(Guid optional = Guid.Empty)
  {
  }
  </code></pre>
  
  <p>But the compiler complains that Guid.Empty is not a compile time constant.</p>
  
  <p>As I don’t wish to change the API I can’t use:</p>
  
  <pre><code> Nullable&lt;Guid&gt;
  </code></pre>