private static IEnumerable <T> AscendantsCore <T, K>(IEnumerable <T> source, Func <T, K> keySelector, Func <T, K> parentKeySelector, Equality <K> equality, K startKey, bool ascendantsOnly = false, int?levelsCount = null)
where T : class
where K : class
{
PwrList <T> list = new PwrList <T>();
T item = source.SingleOrDefault(t => equality(keySelector(t), startKey));
if (item != null && ascendantsOnly)
{
K parentKey = parentKeySelector(item);
item = parentKey != null?source.SingleOrDefault(t => equality(keySelector(t), parentKey)) : null;
}
if (item != null)
{
list.Add(item);
}
for (int passCount = 1; (!levelsCount.HasValue || levelsCount.Value > passCount) && item != null; passCount++)
{
K parentKey = parentKeySelector(item);
item = parentKey != null?source.SingleOrDefault(t => equality(keySelector(t), parentKey)) : null;
if (item != null)
{
list.Add(item);
}
}
return(list.AsEnumerable());
}
public PwrList <T> DequeRangeBack(K key, int count)
{
if (count < 0 || count > InnerList.Count)
{
throw new ArgumentOutOfRangeException("count");
}
var list = new PwrList <T>(count);
var index = InnerList.BinarySearch(t => KeyComparison(KeySelector(t), key), SortingOption.Last);
while (index >= 0 && index < InnerList.Count && KeyComparison(KeySelector(InnerList[index]), key) == 0 && count-- > 0)
{
list.Add(InnerList[index]);
InnerList.RemoveAt(index--);
}
return(list);
}