title: Concat 2 lists with the generic being a class, ignoring duplicated properties?
body: <p>I use to store my data in a double string dictionary, I've now refactored my code to use a <code>DownloadFile</code> class where I can store more than a KeyValue pair.</p>
  
  <p>So this,</p>
  
  <pre><code>Dictionary&lt;string, string&gt; downloads;
  </code></pre>
  
  <p>Becomes</p>
  
  <pre><code>List&lt;DownloadFile&gt; downloads;
  </code></pre>
  
  <p>I use to concat 2 dictionarys, skipping the duplicates like so.</p>
  
  <pre><code>imageUrls = imageUrls.Concat(newImages.Where(x =&gt; !imageUrls.ContainsKey(x.Key))).ToDictionary(x =&gt; x.Key, x =&gt; x.Value);
  </code></pre>
  
  <p>I need to do this with the new system, here is as far as I have got.</p>
  
  <pre><code>imageUrls = imageUrls.Concat(newImages).ToList();
  </code></pre>
  
  <p>I can't access properties inside the DownloadFile class, atleast I don't know how to. Can anybody advise me into a solution for this problem? I couldn't find anything from a google search.</p>
  
  <p>Each class DownloadFile has a property called Address, I simply need to avoid adding duplicated instances of <code>DownloadFile</code> to the main list inside the new images list, ignoring duplicated <code>Address</code> properties.</p>