title: Flatten an Array in C#
body: <p>In C# what is the shortest code to flatten an array?</p>
  
  <p>For example, I want</p>
  
  <pre><code>[[1,2],[2,3],[4,5]]
  </code></pre>
  
  <p>into the array</p>
  
  <pre><code>[1,2,3,4,5]
  </code></pre>
  
  <p>I am looking for the shortest way to do so. </p>