title: LINQ Exception if node don't exists
body: <p>I'm trying to read a xml file and write it to entities in data model. 
  The Xml looks like this :</p>
  
  <pre><code>...
  &lt;item&gt;
     &lt;guid&gt;123456-7890&lt;/guid&gt;
     &lt;enclosure type="image/jpeg" url="http://example.com"/&gt;
  &lt;/item&gt;
  </code></pre>
  
  <p>Sometimes whole enclosure node doesn't exists, so I'm using let in my query, but it breaks:</p>
  
  <pre><code>var items = from xmlitems in xElem2.Descendants("item")
              let node_enclosure = xmlitems.Element("enclosure")
              select new
              {
                   strImageUrl = node_enclosure == null ? "none" : node_enclosure.Attribute("url").Value,
                   strguid = xmlitems.Element("guid").Value,
              };
  </code></pre>
  
  <p>Update: Then I'm trying to save value from xml in Datacontext.</p>
  
  <pre><code>using (var datacontext = new db_RBEntities1())
  {
       foreach (var item in items)
       {
           try
           {                 
                xmltable = new RSSTable();
                xmltable.guid = item.guid;
                xmltable.imageurl= item.strImageUrl;            
                datacontext.RSSTable.AddObject(xmltable);
           }
           catch (EntitySqlException ex)
           {
           }
       }
       datacontext.SaveChanges();
  }
  </code></pre>
  
  <p>Could you help me what's wrong with my query?
  Thanks for your advices!</p>
  
  <p>Regards </p>