Tree items can not be listed

[maninwindow]

I am working on a Windows desktop application that contains interactive window tree like below: (Right window will change by selecting different tree item from the left) What i inspected by UIAVerify is below: When i select tree: When i select one tree item:

My code is below:

Application app = Application.AttachOrLaunch(new System.Diagnostics.ProcessStartInfo(AUT));

 var window = app.GetWindow("Main window ");

 //get all panes

 var panes = window.GetMultiple(SearchCriteria.ByControlType(ControlType.Pane));

 //get contact pane

 var pane_contact = panes[3] as Panel;

 //get option button inside pane

 var button_option = pane_contact.Items[0] as Button;

 button_option.Click();

 //Get window

 var options_Window = window.ModalWindow("window includes tree which is opened from main 
window");

 //Get tree

 var trees = options_Window.Get<Tree>(SearchCriteria.ByControlType(ControlType.Tree));

 var rootNode = trees.Nodes[0] as TreeNode;

  var nodes = rootNode.Nodes;

I can get one tree element in variable trees, but nothing in variable nodes as items. Can anybody explain am i doing the right thing? Why it can't be found? If i was wrong, please share your idea. Thanks in advance.

[maninwindow]

I solved problem myself.Let me share the code to help people who have the same issue.

            //open window
            //// close any open windows
            window.Focus();
            var allOpenWindows = window.GetMultiple(SearchCriteria.ByControlType(ControlType.LookupById(0x50CF6)));
            var windows = app.GetWindows().Where( w =>w.Name != window.Name);
            foreach (var item in windows)
            {
                item.Close();
            }
            windows = app.GetWindows().Where(w => w.Name != window.Name);
            var options_Window = windows.First();

            //Get tree
            var trees = options_Window.Get<Tree>(SearchCriteria.ByControlType(ControlType.Tree));
            //move to the last tab
            for (int i = 0; i <= 13; i++)
            {
                trees.KeyIn(KeyboardInput.SpecialKeys.DOWN);
            }