title: Check if Nullable Guid is empty in c#
body: <p>Quoting from an answer from <a href="https://stackoverflow.com/questions/9837602/why-isnt-there-a-guid-isnullorempty-method">this</a> question.</p>
  
  <blockquote>
    <p>Guid is a value type, so a variable of type Guid can't be null to
    start with.</p>
  </blockquote>
  
  <p>What then if I see this?</p>
  
  <pre><code>public Nullable&lt;System.Guid&gt; SomeProperty { get; set; }
  </code></pre>
  
  <p>how should I check if this is null? Like this?</p>
  
  <pre><code>(SomeProperty == null)
  </code></pre>
  
  <p>or like this?</p>
  
  <pre><code>(SomeProperty == Guid.Empty)
  </code></pre>