Class CompositeNode

public abstract class CompositeNode<T> : CompositeNodeBase, INode, ICompositeNode<T>, ICompositeNode, IEnumerable<T>, IEnumerable where T : INode
{
    public void Add(T node)
    {
        if (node == null) throw new ArgumentNullException(nameof(node));
        if (!_children.Contains(node))
            _children.Add(node);
    }
    IEnumerator<T> IEnumerable<T>.GetEnumerator()
    {
        return _children.OfType<T>().GetEnumerator();
    }
    IEnumerator IEnumerable.GetEnumerator()
    {
        return GetEnumerator();
    }
}

protected CompositeNode(NodeType nodeType)
   {
   }

public T FirstChild
   {
      get;
   }

string dataDir = RunExamples.GetDataDir_Pages();
    Document doc = new Document(dataDir + "Aspose.one", new LoadOptions { LoadHistory = true });
    var history = doc.GetPageHistory(doc.FirstChild);
    for (int i = 0; i < history.Count; i++)
    {
        var historyPage = history[i];
        Console.Write("    {0}. Author: ", i);
        Console.WriteLine("{1}, {2:dd.MM.yyyy hh.mm.ss}",
            historyPage.PageContentRevisionSummary.AuthorMostRecent,
            historyPage.PageContentRevisionSummary.LastModifiedTime);
        Console.Write(historyPage.IsConflictPage ? ", IsConflict: true" : string.Empty);
        if (historyPage.IsConflictPage)
            historyPage.IsConflictPage = false;
    }
    doc.Save(dataDir + "ConflictPageManipulation_out.one", SaveFormat.One);

public override sealed bool IsComposite
    {
        get;
    }

public T LastChild
   {
      get
      {
         var child = this.Children[this.Children.Count - 1];
         return (T)child;
      }
   }

public override void Accept(DocumentVisitor visitor)
   {
      visitor.Visit(this);
   }
This reformatted code follows standard C# conventions, including proper indentation and spacing.

public override T AppendChildFirst<T1>(T1 newChild) where T1 : T
   {
   }

public virtual T AppendChildLast<T1>(T1 newChild) where T1 : T
    {
    }

[Obsolete("Use GetChildNodes<t>() method instead.")]
    public override List<Node> GetChildNodes(NodeType type)
    {
    }

public override List<t1> GetChildNodes<t1>() where T1 : class, INode
{
    var result = new List<t1>();
    foreach (var node in _nodes)
    {
        if (node is t1 child && child.IsDescendantOf(this))
            result.Add(child);
    }
    return result;
}

string dataDir = RunExamples.GetDataDir_Images();
   Document oneFile = new Document(dataDir + "Aspose.one");
   IList<aspose.note.Image> nodes = oneFile.GetChildNodes<aspose.note.Image>();
   foreach (Aspose.Note.Image image in nodes)
   {
       using (MemoryStream stream = new MemoryStream(image.Bytes))
       {
           using (Bitmap bitmap = new Bitmap(stream))
           {
               bitmap.Save(String.Format(dataDir + "{0}", Path.GetFileName(image.FileName)));
           }
       }
   }

string dataDir = RunExamples.GetDataDir_Images();
   Document oneFile = new Document(dataDir + "Aspose.one");
   IList<aspose.note.Image> images = oneFile.GetChildNodes<aspose.note.Image>();
   foreach (Aspose.Note.Image image in images)
   {
      Console.WriteLine("Width: {0}", image.Width);
      Console.WriteLine("Height: {0}", image.Height);
      Console.WriteLine("OriginalWidth: {0}", image.OriginalWidth);
      Console.WriteLine("OriginalHeight: {0}", image.OriginalHeight);
      Console.WriteLine("FileName: {0}", image.FileName);
      Console.WriteLine("LastModifiedTime: {0}", image.LastModifiedTime);
      Console.WriteLine();
   }

public IEnumerator<T> GetEnumerator()
   {
   }

public override T InsertChild<T1>(int index, T1 newChild)
        where T1 : T
    {
    }

public void InsertChildrenRange(int i, IEnumerable<t> newChildren)
   {
   }

public void InsertChildrenRange(int i, params T[] newChildren)
{
}

public T RemoveChild<T>(T oldChild) where T : class
   {
   }