C#

public class Test
{
    private int internalValue;
    public Test(int value)
    {
        internalValue = value;
    }

    public static bool operator ==(Test test1, Test test2)
    {
        object o1 = test1;
        object o2 = test2;
        if (o1 == null || o2 == null)
            return (o1 == null && o2 == null);
        return test1.internalValue == test2.internalValue;
    }
    public static bool operator !=(Test test1, Test test2)
    {
        return !(test1 == test2);
    }
}

public static bool operator ==(UserList userlist1, UserList userlist2)
{
if (userlist1 == null) return false;
....
}

public class TreeNode 
{
    public string Code { get; set; }
    public string Text { get; set; }
    public List<TreeNode> Children { get; set }

    public TreeNode()  
    {
         Children = new List<TreeNode>();
    }
}

public TreeNode Populate(XDocument doc)
{
    var retVal = (from treeNode in doc.Descendants("TreeNode")
                select new TreeNode()
                           {
                               Code = treeNode.Attribute("Code").Value,
                               Text = treeNode.Attribute("Text").Value
                           }).SingleOrDefault();
    retVal.Children = _Recurse((from treeNode in doc.Descendants("TreeNode")
                               select treeNode).SingleOrDefault());
    return retVal; 
}

private static List<TreeNode> _Recurse(XContainer root)
{
    List<TreeNode> retVal = new List<TreeNode>();
    var children = from child in root.Descendants("TreeNode") select child;
    foreach(var child in children)
    {
        TreeNode node = new TreeNode
                            {
                                Code = child.Attribute("Code").Value,
                                Text = child.Attribute("Text").Value,
                                Children = _Recurse(child)
                            };
        retVal.Add(node);
    }
    return retVal;
}

  static void SetVisible(Control ctrl, bool visible)
  {
      if (ctrl.InvokeRequired)
      {
          object[] params_list = new object[] { ctrl, visible };
          ctrl.Invoke(new SetVisibleDelegate(SetVisible), params_list);

      }
      else
      {
          ctrl.Visible = visible;
      }
}