public TResult TryGetElementAt(int index, out bool found)
{
bool sourceFound;
TSource input = _source.TryGetElementAt(index, out sourceFound);
found = sourceFound;
return(sourceFound ? _selector(input) : default(TResult));
}
public static TSource ElementAt <TSource>(this IEnumerable <TSource> source, int index)
{
if (source == null)
{
throw Error.ArgumentNull(nameof(source));
}
IPartition <TSource> partition = source as IPartition <TSource>;
if (partition != null)
{
bool found;
TSource element = partition.TryGetElementAt(index, out found);
if (found)
{
return(element);
}
}
else
{
IList <TSource> list = source as IList <TSource>;
if (list != null)
{
return(list[index]);
}
if (index >= 0)
{
using (IEnumerator <TSource> e = source.GetEnumerator())
{
while (e.MoveNext())
{
if (index == 0)
{
return(e.Current);
}
index--;
}
}
}
}
throw Error.ArgumentOutOfRange(nameof(index));
}
public static TSource ElementAtOrDefault <TSource>(this IEnumerable <TSource> source, int index)
{
if (source == null)
{
throw Error.ArgumentNull("source");
}
IPartition <TSource> partition = source as IPartition <TSource>;
if (partition != null)
{
bool found;
return(partition.TryGetElementAt(index, out found));
}
if (index >= 0)
{
IList <TSource> list = source as IList <TSource>;
if (list != null)
{
if (index < list.Count)
{
return(list[index]);
}
}
else
{
using (IEnumerator <TSource> e = source.GetEnumerator())
{
while (e.MoveNext())
{
if (index == 0)
{
return(e.Current);
}
index--;
}
}
}
}
return(default(TSource));
}
