public static int Count <TEnumerable, TEnumerator, TSource>(this TEnumerable source)
where TEnumerable : IEnumerable <TSource>
where TEnumerator : IEnumerator <TSource>
{
if (source == null)
{
ThrowSourceNull();
}
return(CountCache <TEnumerable, TEnumerator, TSource> .count(source));
void ThrowSourceNull() => throw new ArgumentNullException(nameof(source));
}
public static long Count <TEnumerable, TSource>(this TEnumerable source) where TEnumerable : IEnumerable <TSource>
{
if (source == null)
{
throw new ArgumentNullException(nameof(source));
}
if (source is ICollection <TSource> collection)
{
return(collection.Count);
}
if (source is IReadOnlyCollection <TSource> readOnlyCollection)
{
return(readOnlyCollection.Count);
}
return(CountCache <TEnumerable, TSource> .count(source));
}