if (obj == null || parentObj == null || numerator == null)
	return string.Concat(prefix, current);

var doc = obj.Document;
if (doc.Extensions.EngineeringChangesManager.State >= TechEngineeringChangesTechnologyState.Approved)
{

	object childFilter = doc.Model.Filters[numerator.Children] as object ?? doc.Model.Classes[numerator.Children];
	string attrName = numerator.AttributeName;
	var children = parentObj.Children.Find(childFilter).ToList();

	int objIndex = children.IndexOf(obj);

	int prevValue = 0;
	int nextValue = 0;
	int currentValue;

	Func<TechObject, int> getNumberFunc = (o) =>
	{
		if (o == null)
			return 0;
		var stringValue = o.Attributes[attrName].Value.ToString();
		int result = 0;
		if (!string.IsNullOrEmpty(prefix))
			stringValue = stringValue.Replace(prefix, string.Empty);
		int.TryParse(stringValue, out result);
		return result;
	};

	currentValue = getNumberFunc(obj);

	if (objIndex > 0)
		prevValue = getNumberFunc(children[objIndex - 1]);

	int nextObjectIndex = objIndex + 1;
	while (nextObjectIndex < children.Count)
	{
		nextValue = getNumberFunc(children[nextObjectIndex]);
		if (nextValue > prevValue)
			break;
		nextObjectIndex++;
	}

	if (children.Count > 1 && 
			currentValue > prevValue &&
			nextValue <= prevValue && prevValue > 0)
		return obj.Attributes[attrName].Value.ToString();

	if (nextValue <= prevValue)
		nextValue = 0;
	
	if (children.Count > 1 &&
			currentValue > prevValue &&
			nextObjectIndex - objIndex == 1 &&
			(currentValue < nextValue || nextValue == 0))
		return obj.Attributes[attrName].Value.ToString();

	int step = (nextValue == 0) ? numerator.Step : (nextValue - prevValue) / 2;

	// Получает значение
	int value = (step > 0) ? prevValue + step : prevValue + 1;

	if (objIndex < children.Count - 1)
	{
		nextValue = getNumberFunc(children[objIndex + 1]);
		if (nextValue <= value)
		{
			obj.Attributes[attrName].Value = prefix + value.ToString("D" + numerator.MaxLength);
			// для передачи в функцию Renumerate используем индекс объекта в общем, неограниченном фильтром списке дочерних объектов
			objIndex = parentObj.Children.IndexOf(obj);
			obj.Document.Extensions.NumerationService.Renumerate(parentObj, objIndex + 1, objIndex + 1);
		}
	}

	return prefix + value.ToString("D" + numerator.MaxLength);
}

return string.Concat(prefix, current);