public static int Count <TSource>(this IEnumerable <TSource> source)
{
switch (source)
{
case TSource[] array:
return(array.Length);
case IReadOnlyCollection <TSource> collection:
return(collection.Count);
default:
return(CountDowncasted <IEnumerable <TSource>, TSource> .Count(source));
}
}
public static int Count <TSource>(this IEnumerable <TSource> source, Func <TSource, bool> predicate) => CountDowncasted <IEnumerable <TSource>, TSource> .Count(source, predicate);