title: How to merge two dictionaries in C# with duplicates
body: <p>Is there a way in C# to merge two dictionaries? I have two dictionaries that may has the same keys, but I am looking for a way to merge them so, in the end there is a dictionary with one key and the values from both the dictionaries merged.
  I found the following code but it does not handle duplicates.</p>
  
  <pre><code>Dictionary Mydictionary&lt;string, string[]&gt; = new Dictionary&lt;string, string[]&gt;();
  Mydictonary.Union(secondDictionary).ToDictionary( pair =&gt; pair.Key, pair =&gt; pair.Value);
  </code></pre>