Getting value as 'Null' and count as 0 while finding/locating sub element/children within app window of windows 8.1 metro style app.

Getting value as 'Null' and count as 0 while finding/locating sub element/children within app window of windows 8.1 metro style app.
We have followed below links:
http://guriyakalyani.blogspot.in/
http://blog.frogslayer.com/windows-store-applications-and-automated-testing-part-two/
We got App User Model ID of app from registry and we are able to launch windows 8.1 metro style app using code mentioned above links.

We are able to get root element 'desktop' using following code:

AutomationElement aeDesktop = AutomationElement.RootElement;

Also we are able to locate app window using following code:
 Condition appCondition =
            new PropertyCondition(AutomationElement.NameProperty,
                                "IT Tech Books", PropertyConditionFlags.IgnoreCase);
            AutomationElement aeAppWindow =
                                      aeDesktop.FindFirst(TreeScope.Descendants,
                                      appCondition);
            Thread.Sleep(1000);

But we are getting value of aePane as 'Null' and count as 0 while finding/locating sub element/children within above app window.

We used following code for the same:
            AutomationElementCollection aePane =
                 aeAppWindow.FindAll(TreeScope.Children, new PropertyCondition(AutomationElement.AutomationIdProperty, "btnGoToLibrary", PropertyConditionFlags.IgnoreCase));

Here IT Tech Books is a windows 8.1 metro style application for which we need to do UI automation

Also I have uploaded file on OneDrive is as follows:

https://onedrive.live.com/redir?resid=320F3D6BD73595AF%21106

This c# project where we tried UI automation for Microsoft Lync application. We are getting value for variable 'aePane' as Null.

Thanks,

Mrudula