递归寻找节点

    public class FileNode : PropertyChangedBase
    {
        public FileNode()
        {
            this.Files = new ObservableCollection<FileNode>();
            this.IsFile = false;
        }

        private string _name = string.Empty;

        public string Name
        {
            get { return _name; }
            set
            {
                _name = value;
                NotifyOfPropertyChange(nameof(Name));
            }
        }

        private string _fullPath;

        public string FullPath
        {
            get => _fullPath;
            set
            {
                _fullPath = value;
                NotifyOfPropertyChange(nameof(FullPath));
            }
        }

        public FileNode Parent { get; set; }
        public ObservableCollection<FileNode> Files { get; set; }
        public bool IsFile { get; set; }
        public string PrefixPath { get; set; }

        private bool _isSelected;

        public bool IsSelected
        {
            get => _isSelected;
            set
            {
                _isSelected = value;
                NotifyOfPropertyChange(nameof(IsSelected));
            }
        }

        private bool _isExpanded;

        public bool IsExpanded
        {
            get => _isExpanded;
            set
            {
                _isExpanded = value;
                NotifyOfPropertyChange(nameof(IsExpanded));
            }
        }

        private Visibility _Visibility = Visibility.Visible;
        public Visibility Visibility
        { get { return _Visibility; } set { _Visibility = value; NotifyOfPropertyChange(nameof(Visibility)); } }
    }
	
        private FileNode FindFileNodeWithFullPath(IList<FileNode> nodes, string fullPath)
        {
            foreach (var file in nodes)
            {
                if (file.FullPath == fullPath)
                {
                    return file;
                }

                if (file.Files != null)
                {
                    var subFile = FindFileNodeWithFullPath(file.Files, fullPath);
                    if (subFile != null)
                    {
                        return subFile;
                    }
                }
            }
            return null;
        }