Umbraco v8: Helpful methods to query children of an IContent

IContentExtensions.cs

public static class IContentExtensions {
  public static bool HasChildren(this IContent content)
  {
      return Umbraco.Core.Composing.Current.Services.ContentService.HasChildren(content.Id);
  }

  public static int CountChildren(this IContent content, string childDocType = null)
  {
      return Umbraco.Core.Composing.Current.Services.ContentService.CountChildren(content.Id, childDocType);
  }

  /// <summary>
  /// Get last children
  /// </summary>
  /// <param name="content"></param>
  /// <param name="order">Default is sortOrder</param>
  /// <param name="predicate">filter</param>
  /// <returns></returns>
  public static IContent LastChildren(this IContent content,
      string order = "sortOrder", Direction direction = Direction.Ascending,
      Expression<Func<IContent, bool>> predicate = null)
  {
      long total;
      IQuery<IContent> filter = null;
      if (predicate != null)
      {
          var _sqlContext = Umbraco.Core.Composing.Current.Factory.GetInstance<ISqlContext>();
          filter = _sqlContext.Query<IContent>().Where(predicate);
      }

      Ordering ordering = null;
      if (!string.IsNullOrEmpty(order))
      {
          var real_direction = direction == Direction.Ascending ? Direction.Descending : Direction.Ascending;
          ordering = Ordering.By(order, real_direction, null, false);
      }

      return Umbraco.Core.Composing.Current.Services.ContentService.GetPagedChildren(content.Id, 0, 1, out total, filter, ordering).FirstOrDefault();
  }

  /// <summary>
  /// Get last children
  /// </summary>
  /// <param name="content"></param>
  /// <param name="order">Default is sortOrder</param>
  /// <param name="predicate">filter</param>
  /// <returns></returns>
  public static IContent FirstChildren(this IContent content,
      string order = "sortOrder", Direction direction = Direction.Ascending,
      Expression<Func<IContent, bool>> predicate = null)
  {
      long total;
      IQuery<IContent> filter = null;
      if (predicate != null)
      {
          var _sqlContext = Umbraco.Core.Composing.Current.Factory.GetInstance<ISqlContext>();
          filter = _sqlContext.Query<IContent>().Where(predicate);
      }

      Ordering ordering = null;
      if (!string.IsNullOrEmpty(order))
      {
          ordering = Ordering.By(order, direction, null, false);
      }

      return Umbraco.Core.Composing.Current.Services.ContentService.GetPagedChildren(content.Id, 0, 1, out total, filter, ordering).FirstOrDefault();
  }

  /// <summary>
  /// 
  /// </summary>
  /// <param name="parent"></param>
  /// <param name="predicate"></param>
  /// <returns></returns>
  public static IContent IsExistChildren(this IContent parent, Expression<Func<IContent, bool>> predicate = null)
  {
      long total;

      IQuery<IContent> filter = null;
      if (predicate != null)
      {
          var _sqlContext = Umbraco.Core.Composing.Current.Factory.GetInstance<ISqlContext>();
          filter = _sqlContext.Query<IContent>().Where(predicate);
      }

      var result = Umbraco.Core.Composing.Current.Services.ContentService.GetPagedChildren(parent.Id, 0, 1, out total, filter);
      return result.FirstOrDefault();
  }

  public static IEnumerable<IContent> Children(this IContent parent, int top, Expression<Func<IContent, bool>> predicate = null,
      string order = "sortOrder",
      Direction direction = Direction.Ascending)
  {
      if (top <= 0) return null;

      long total;
      IQuery<IContent> filter = null;
      if (predicate != null)
      {
          var _sqlContext = Umbraco.Core.Composing.Current.Factory.GetInstance<ISqlContext>();
          filter = _sqlContext.Query<IContent>().Where(predicate);
      }
      Ordering ordering = null;
      if (!string.IsNullOrEmpty(order))
      {
          ordering = Ordering.By(order, direction, null, false);
      }

      return Umbraco.Core.Composing.Current.Services.ContentService.GetPagedChildren(parent.Id, 0, top, out total, filter);
  }
}