title: Compare two dictionaries by key and create a new one where keys don’t match
body: <p>I have two dictionaries of type (string, string). I need to compare these and create a new dictionary where just the Keys don’t match. For example, given these values</p>
  
  <pre><code>Dictionary A
  
  Key  Value
  =========
  A      B
  C      D
  
  
  Dictionary B
  
  Key  Value
  =========
  A      Z
  E      D
  </code></pre>
  
  <p>I need to create a new dictionary that would just have a single entry of (E,D)</p>
  
  <p>==== Edit ====</p>
  
  <p>When the compare is done I am just involving the keys, the values are of no interest. The key values are just strings so don't link to other objects. There is no hidden mapping etc. The "Value" only comes into play when I have the resulting dictionary as this is then used in my program. Think of this problem as if the values didn't exist and I was just trying to get a list of keys that are in dictionary "B" but not in "dictionary "A". I am not interested in key "C" as I am just interested in the unique keys that are just in dictionary "B" but not in dictionary "A".</p>