private void checkChildren(ModelDirectory dir)
 {
     if (dir.isParent())
     {
         List <ModelDirectory> children = dir.children;
         foreach (ModelDirectory child in children)
         {
             TreeNode[] nodes = treeView1.Nodes.Find(child.id, true); //Directory.id to jest TreeNode.Name
             nodes[0].Checked = true;                                 //zawsze jest tylko jedna, bo index jest unikalny
         }
     }
 }
        private TreeNode createDirectoryNode(ModelDirectory dir)
        {
            var dirNode = new TreeNode(dir.name);

            try
            {
                dirNode.Name = dir.id;
                if (dir.isParent())
                {
                    foreach (var child in dir.children)
                    {
                        dirNode.Nodes.Add(createDirectoryNode(child));
                    }
                }
            }
            catch (NullReferenceException ex)
            {
                MyMessageBox.display(ex.Message + "  \r\nbłąd createDirectoryNode");
            }
            return(dirNode);
        }