title: An expression tree may not contain a call or invocation that uses optional arguments
body: <blockquote>
    <p>An expression tree may not contain a call or invocation that uses
    optional arguments</p>
  </blockquote>
  
  <pre><code>return this.RedirectToAction&lt;MerchantController&gt;(x =&gt; x.Edit(merchantId));
  </code></pre>
  
  <p>Where edit had a second, nullable argument.</p>
  
  <p>Why is this?</p>