title: LINQ OrderBy versus ThenBy
body: <p>Can anyone explain what the difference is between:</p>
  
  <pre><code>tmp = invoices.InvoiceCollection
                .OrderBy(sort1 =&gt; sort1.InvoiceOwner.LastName)
                .OrderBy(sort2 =&gt; sort2.InvoiceOwner.FirstName)
                .OrderBy(sort3 =&gt; sort3.InvoiceID);
  </code></pre>
  
  <p>and</p>
  
  <pre><code>tmp = invoices.InvoiceCollection
                .OrderBy(sort1 =&gt; sort1.InvoiceOwner.LastName)
                .ThenBy(sort2 =&gt; sort2.InvoiceOwner.FirstName)
                .ThenBy(sort3 =&gt; sort3.InvoiceID);
  </code></pre>
  
  <p>Which is the correct approach if I wish to order by 3 items of data?</p>