C#

void SelectData(long start, long end)
{
  _selected.Add(new Range(start, end));
  if (_selected.Count > 1)
    RemoveRangeRedundancies();
}

void RemoveRangeRedundancies()
{
  foreach (Range rr in _selected)
  {
    foreach (Range r in _selected)
    {
      if (rr == r) continue;

      if (rr.MinValue >= r.MinValue && rr.MaxValue <= r.MaxValue)  //selection completely inside an already selected range of data.
      {
        _selected.Remove(rr);
        continue;
      }

      if (rr.MinValue <= r.MinValue && rr.MaxValue >= r.MaxValue) //selection bigger on both or one rr.MaxValue
      {
        _selected.Remove(r);
        continue;
      }

      //selection bigger or connected to the left (join)
      if (rr.MinValue < r.MinValue && (rr.MaxValue >= r.MinValue - 1) && rr.MaxValue <= r.MaxValue)
      {
        Range newRange = new Range(rr.MinValue, r.MaxValue);
        _selected.Remove(rr);
        _selected.Remove(r);
        _selected.Add(newRange);
        continue;
      }

      //selection bigger or connected to the right (join)
      if (rr.MinValue >= r.MinValue && (rr.MinValue <= r.MaxValue + 1) && rr.MaxValue > r.MaxValue)
      {
        Range newRange = new Range(r.MinValue, rr.MaxValue);
        _selected.Remove(rr);
        _selected.Remove(r);
        _selected.Add(newRange);
        continue;
      }
    }
  }
}