title: Merge two dictionaries in C#
body: <p>Knowing this <a href="https://stackoverflow.com/questions/294138/merging-dictionaries-in-c-sharp">question's answer</a>, what is the way to join 2 (only) dictionaries (.Net 4.5)?</p>
  
  <p>Duplicates not admitted, the first one wins (see example bellow).</p>
  
  <pre><code>using System;
  using System.Linq;
  using System.Collections.Generic;
  
  public class Program
  {
      public static void Main()
      {
          var d1 = new Dictionary&lt;int, string&gt;();
          var d2 = new Dictionary&lt;int, string&gt;();
          // combine both, keep first duplicate only 
          var result = d1.XXX?(d2); 
  
      }
  }
  </code></pre>
  
  <p>say </p>
  
  <p><code>[&lt;1,'a'&gt;, &lt;2, 'b'&gt;]</code> + <code>[&lt;3,'c'&gt;, &lt;1, 'x'&gt;]</code> = > <code>[&lt;1,'a'&gt;, &lt;2, 'b'&gt;, &lt;3,'c'&gt;]</code></p>