public class NotNullOrEmptyCollectionAttribute : ValidationAttribute
{
    private readonly int _length;

    public NotNullOrEmptyCollectionAttribute(int length)
    {
        _length = length;
    }

    public NotNullOrEmptyCollectionAttribute()
    {
        _length = -1;
    }

    public override bool IsValid(object value)
    {
        return value switch
        {
            ICollection collection when _length > -1 => collection.Count >= _length,
            ICollection collection => collection.Count != 0,
            _ => value is IEnumerable enumerable && enumerable.GetEnumerator().MoveNext()
        };
    }
}