title: Getting i-th value from a SortedList or SortedDictionary
body: <p>I have a sorted collection of objects (it can be either SortedList or SortedDictionary, I will use it mainly for reading so add performance is not that important). How can I get the i-th value?</p>
  
  <p>So e.g. when I have numbers 1, 2, 3, 4, 5 in the collection and I want the median (so 3 in this example), how can I do it?</p>