title: LINQ subquery with AND operator displays no results
body: <p>Me again...
  I have an XML File that contains different categories which I would like to query for different attributes.</p>
  
  <pre><code>        &lt;item&gt;      
              &lt;title&gt;Industries&lt;/title&gt;      
              &lt;category type="Channel"&gt;Automotive&lt;/category&gt;      
              &lt;category type="Type"&gt;Cars&lt;/category&gt;      
              &lt;category type="Token"&gt;Article&lt;/category&gt;      
              &lt;category type="SpecialToken"&gt;News&lt;/category&gt;      
              &lt;guid&gt;637f0dd7-57a0-4001-8272-f0fba60feba1&lt;/guid&gt;
          &lt;/item&gt;
  </code></pre>
  
  <p>IN SQL I would write something like.</p>
  
  <pre><code>select * from articles where channel = 'Automative' AND type = 'Cars' etc. etc.
  </code></pre>
  
  <p>How can I achieve this with linq?
  I tried the following query but it returns null. If I combine the two attributes with the "OR" || operator I would get the results, but with all double results if an item matches both criteria.</p>
  
  <pre><code>var articleList = (from item in doc.Descendants("item")
  
                           from _category in item.Elements("category")
                           where _category.Value == valueCboChannel &amp;&amp; _category.Attribute("domain").Value == "Channel"
                           &amp;&amp; (_category.Value == valueCboSubChannel &amp;&amp; _category.Attribute("domain").Value == "SubChannel")
  
                           select new
                           {
  
                               Title = item.Element("title").Value,
                               Guid= item.Element("guid").Value,
                               description = item.Element("description").Value,
                               link = item.Element("link").Value
                           }).ToList();
  
              ListView1.DataSource = articleList;
              ListView1.DataBind();               
  </code></pre>