public static bool HasDuplicates <T>(this IEnumerable <T> source)
{
if (source == null)
{
throw new ArgumentNullException(nameof(source));
}
return(source.HasDuplicates(EqualityComparer <T> .Default));
}
public static bool HasDuplicates <T>(this IEnumerable <T> enumerable)
{
return(enumerable.HasDuplicates(e => e));
}