title: How to use DATEADD over column in LINQ - DateAdd is not recognized by LINQ
body: <p>I am trying to invalidate requests of friendship that were reponded less than 30 days ago.</p>
  
  <pre><code>var requestIgnored = context.Request
      .Where(c =&gt; c.IdRequest == result.IdRequest 
               &amp;&amp; c.IdRequestTypes == 1 
               &amp;&amp; c.Accepted == false 
               &amp;&amp; DateTime.Now &lt;= (((DateTime)c.DateResponse).AddDays(30)))
     .SingleOrDefault();
  </code></pre>
  
  <p><code>c.DateResponse</code> is of type <code>DateTime?</code>. The error I am having is : </p>
  
  <blockquote>
    <p>LINQ does not recognize the command .AddDays</p>
  </blockquote>