title: LINQ select where item is not in list
body: <p>i need to insert items that are not in db. so i'm trying to run the following (which doesn't work):</p>
  
  <pre><code> foreach(var rep in model.Reps.Where(x =&gt; x.Value != 
      this.dictionaryItemRepository.List().Select(y =&gt; y.Value)))
  </code></pre>
  
  <p>where model.Reps is:</p>
  
  <pre><code> public ICollection&lt;DictionaryItemBrand&gt; Reps { get; set; }
  </code></pre>
  
  <p>returned from model binder</p>
  
  <p>I'm trying to do a foreach loop -> <strong>select all items from model.Reps that do NOT yet exist in repository.</strong></p>
  
  <p>how can i do it?
  thanks</p>