public static TSource FirstOrDefault <TSource>(this IEnumerable <TSource> source)
{
if (source == null)
{
throw Error.ArgumentNull("source");
}
IPartition <TSource> partition = source as IPartition <TSource>;
if (partition != null)
{
bool found;
return(partition.TryGetFirst(out found));
}
IList <TSource> list = source as IList <TSource>;
if (list != null)
{
if (list.Count > 0)
{
return(list[0]);
}
}
else
{
using (IEnumerator <TSource> e = source.GetEnumerator())
{
if (e.MoveNext())
{
return(e.Current);
}
}
}
return(default(TSource));
}
public TResult TryGetFirst(out bool found)
{
bool sourceFound;
TSource input = _source.TryGetFirst(out sourceFound);
found = sourceFound;
return(sourceFound ? _selector(input) : default(TResult));
}
public static TSource First <TSource>(this IEnumerable <TSource> source)
{
if (source == null)
{
throw Error.ArgumentNull(nameof(source));
}
IPartition <TSource> partition = source as IPartition <TSource>;
if (partition != null)
{
bool found;
TSource first = partition.TryGetFirst(out found);
if (found)
{
return(first);
}
}
else
{
IList <TSource> list = source as IList <TSource>;
if (list != null)
{
if (list.Count > 0)
{
return(list[0]);
}
}
else
{
using (IEnumerator <TSource> e = source.GetEnumerator())
{
if (e.MoveNext())
{
return(e.Current);
}
}
}
}
throw Error.NoElements();
}
internal static TSource TryGetFirst <TSource>(this IEnumerable <TSource> source, out bool found)
{
if (source == null)
{
throw Error.ArgumentNull(nameof(source));
}
IPartition <TSource> partition = source as IPartition <TSource>;
if (partition != null)
{
return(partition.TryGetFirst(out found));
}
IList <TSource> list = source as IList <TSource>;
if (list != null)
{
if (list.Count > 0)
{
found = true;
return(list[0]);
}
}
else
{
using (IEnumerator <TSource> e = source.GetEnumerator())
{
if (e.MoveNext())
{
found = true;
return(e.Current);
}
}
}
found = false;
return(default(TSource));
}