HTMLWindow::Parent Property

public void CodeExample(DTE2 dte)
{
   // Make sure you have an open HTML document before running this example.
    try
    {
        if (dte.ActiveDocument.ActiveWindow.Object is HTMLWindow)
        {
            HTMLWindow htmlwin;
            string msg = "";
            htmlwin = dte.ActiveDocument.ActiveWindow.Object as HTMLWindow;
            // Show the related application object's name.
            msg += "The application containing this HTMLWindow is " + htmlwin.DTE.Name;
            // Show the HTMLWindow's parent object.
            msg += "\nThe HTMLWindow's parent object is " + htmlwin.Parent.Type.ToString();
            MessageBox.Show(msg);
        }
    }
    catch(Exception ex)
    {
        MessageBox.Show(ex.Message);
    }
}