title: Add element to list before specific element
body: <p>I have a list of items, lets say 100 items. I need to add another element before the existing element that matches my condition. What is the fastest way and the most performance optimized to do this? 
  ie.:</p>
  
  <pre><code>foreach (var i in myList)
  {
      if (myList[i].value == "myValue")
      {
          myList[i-1] add ("someOtherValue")
      }
  }
  </code></pre>
  
  <p>Maybe i should use other container? </p>