BoxFolderTreeBuilder.cs

public class BoxFolderTreeBuilder
{
    public BoxClient BoxClient { get; set; }
    public string RootFolderId { get; set; }
    public int MaxDepth { get; set; }

    public BoxFolderTreeBuilder(BoxClient boxClient, string rootFolderId = "0", int maxDepth = -1)
    {
        this.BoxClient = boxClient;
        this.RootFolderId = rootFolderId;
        this.MaxDepth = maxDepth;
    }

    public async Task<BoxFolderTree> BuildFlatLists()
    {
        var tree = new BoxFolderTree
        {
            RootId = this.RootFolderId,
            Files = new List<BoxFolderTreeItem>(),
            Folders = new List<BoxFolderTreeFolder>()
        };
        var rootFolderItems = await this.BoxClient.FoldersManager.GetFolderItemsAsync(this.RootFolderId, limit: 1000, autoPaginate: true);
        var rootFolderChildren = new List<BoxFolderTreeFolder>();
        foreach (var item in rootFolderItems.Entries)
        {
            var folderTreeItem = new BoxFolderTreeItem(item);
            folderTreeItem.Path = $"{this.RootFolderId}";
            if (item.Type == "file")
            {
                tree.Files.Add(folderTreeItem);
            }
            else if (item.Type == "folder")
            {
                var childFolder = new BoxFolderTreeFolder(folderTreeItem);
                tree.Folders.Add(new BoxFolderTreeFolder(folderTreeItem));
                rootFolderChildren.Add(childFolder);
            }
        }
        tree = await Dive(tree, rootFolderChildren, 1);
        return tree;
    }

    private async Task<BoxFolderTree> Dive(BoxFolderTree tree,
        List<BoxFolderTreeFolder> children, int currentDepth)
    {
        if (InTooDeep(currentDepth))
        {
            return tree;
        }
        else
        {
            currentDepth++;
            var additionalChildren = new List<BoxFolderTreeFolder>();
            foreach (var child in children)
            {
                var folderItems = await this.BoxClient.FoldersManager.GetFolderItemsAsync(child.Item.Id, limit: 1000, autoPaginate: true);
                var foundFolder = tree.Folders.FindIndex((f) =>
                {
                    return f.Item.Id == child.Item.Id;
                });
                foreach (var item in folderItems.Entries)
                {
                    if (foundFolder >= 0)
                    {
                        tree.Folders[foundFolder].Children.Add(item);
                    }
                    var folderTreeItem = new BoxFolderTreeItem(item);
                    folderTreeItem.Path = $"{child.Path}/{child.Item.Id}";
                    if (item.Type == "file")
                    {
                        tree.Files.Add(folderTreeItem);
                    }
                    else if (item.Type == "folder")
                    {
                        var childFolder = new BoxFolderTreeFolder(folderTreeItem);
                        tree.Folders.Add(new BoxFolderTreeFolder(folderTreeItem));
                        additionalChildren.Add(childFolder);
                    }
                }
            }
            if (additionalChildren.Count == 0)
            {
                return tree;
            }
            else
            {
                return await Dive(tree, additionalChildren, currentDepth);
            }
        }
    }

    private bool InTooDeep(int depthCount)
    {
        if (this.MaxDepth < 0)
        {
            return false;
        }
        else
        {
            return (depthCount >= this.MaxDepth);
        }
    }
    public class BoxFolderTreeItem
    {
        [JsonProperty(PropertyName = "item")]
        public BoxItem Item { get; set; }

        [JsonProperty(PropertyName = "path")]
        public string Path { get; set; }
        public BoxFolderTreeItem(BoxItem item)
        {
            Item = item;
        }
    }
    public class BoxFolderTreeFolder : BoxFolderTreeItem
    {
        public BoxFolderTreeFolder(BoxFolderTreeItem item) : base(item.Item)
        {
            this.Path = item.Path;
        }

        [JsonProperty(PropertyName = "children")]
        public List<BoxItem> Children { get; set; } = new List<BoxItem>();
    }
    public class BoxFolderTree
    {
        [JsonProperty(PropertyName = "rootId")]
        public string RootId { get; set; }
        [JsonProperty(PropertyName = "files")]
        public List<BoxFolderTreeItem> Files { get; set; }

        [JsonProperty(PropertyName = "folders")]
        public List<BoxFolderTreeFolder> Folders { get; set; }

    }
}