Silverlight Auto Complete Treeview

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;
using System.Xml.Linq;
using System.Collections.ObjectModel;


namespace AutoCompleteTextBox
{
    public partial class MainPage : UserControl
    {

        #region Variable Declarations
            TreeViewItem tv;
            HierarchicalCity selectedTV;
            HierarchicalCity SelectedClass;
            bool selectedText;
            bool IsTextboxFocus = false;
            long LastTicks;
        #endregion
        public MainPage()
        {
            InitializeComponent();
            XDocument loaded = XDocument.Load("City.xml");
            inputBox.ItemsSource = from x in loaded.Descendants("Row")
                                   select (string)x.Attribute("CityName");
            tvData.ItemsSource = Model.GetData();
        }

#region TreeView Events

        private void tvData_SelectedItemChanged(object sender, RoutedPropertyChangedEventArgs<object> e)
        {
            if (tvData.SelectedItem != null)
            {
                if (tvData.SelectedItem.GetType().ToString() == "AutoCompleteTextBox.HierarchicalCity")
                {
                    tv = tvData.ContainerFromItem(tvData.SelectedItem);
                    if (IsTextboxFocus == false)
                    {
                        txtCity.Text = ((HierarchicalCity)tvData.SelectedItem).CityName;
                        selectedText = true;
                    }
                    SelectedClass = (HierarchicalCity)tvData.SelectedItem;
                }
                else if (tvData.SelectedItem.GetType().ToString() == "AutoCompleteTextBox.SilverlightTreeViewItem")
                {
                    tv = (TreeViewItem)tvData.SelectedItem;
                }
            }
        }

        private void tvData_KeyDown(object sender, KeyEventArgs e)
        {
            if (e.Key == Key.Escape || e.Key == Key.Enter)
            {
                if (e.Key == Key.Enter && SelectedClass != null)
                {
                    txtCity.Text = SelectedClass.CityName;
                    selectedText = true;
                }
                txtCity.Focus();
                HideTreeview();
            }
        }

        private void tvData_GotFocus(object sender, RoutedEventArgs e)
        {
            GoToItem();
        }

        private void tvData_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
        {
            if ((DateTime.Now.Ticks - LastTicks) < 2310000)
            {
                if (SelectedClass != null)
                {
                    selectedText = true;
                    txtCity.Text = SelectedClass.CityName;
                }
                txtCity.Focus();
                HideTreeview();
                //PopupControl.IsOpen = false;
            }
            LastTicks = DateTime.Now.Ticks;
            //if (tv != null)
            //    tv.Focus();
        }

        private void tvData_LostFocus(object sender, RoutedEventArgs e)
        {
            CheckFocus();
        }

        #endregion

#region Other Functions

        void CheckFocus()
        {
            
            DependencyObject dp = ((DependencyObject)System.Windows.Input.FocusManager.GetFocusedElement());
            if (dp != null)
            {
                if (((Control)dp).Name == "txtCity" || dp.GetType().Name == "SilverlightTreeViewItem" || dp.GetType().Name == "SilverlightTreeView")
                {
                }
                else
                {
                    HideTreeview();
                }
            }
            else
            {
                HideTreeview();
            }
        }

        private void HideTreeview()
        {
            PopupControl.IsOpen = false;
            tv = null;
            SelectedClass = null;
            foreach (HierarchicalCity item in tvData.Items)
            {
                item.CollapseAll();
            }
        }

        private void ReturnConditions(string val)
        {
            selectedTV = null;
            for (int i = 0; i < Model.GetCurrentData().Count; i++)
            {


                if (Model.GetCurrentData()[i].CityName.StartsWith(val, StringComparison.OrdinalIgnoreCase))
                {
                    selectedTV = Model.GetCurrentData()[i];
                    ExpandAllParents(Model.GetCurrentData()[i]);
                }
                else if (Model.GetCurrentData()[i].SubClass != null)
                {
                    ReturnChildconditionsRecursively(Model.GetCurrentData()[i].SubClass, val);
                }
            }
            if (selectedTV == null)
            {
                HideTreeview();
            }
        }
        private void ReturnChildconditionsRecursively(ObservableCollection<HierarchicalCity> lst,string val)
        {
            for (int j = 0; j < lst.Count; j++)
            {
                if (lst[j].CityName.StartsWith(val,StringComparison.OrdinalIgnoreCase))
                {
                    selectedTV = lst[j];
                    ExpandAllParents(lst[j]);
                    break;
                }
                else if (lst[j].SubClass != null)
                {
                    ReturnChildconditionsRecursively(lst[j].SubClass,val);
                }
            }

        }

        private void ExpandAllParents(HierarchicalCity t)
        {
            SelectedClass = t;
            foreach (HierarchicalCity item in tvData.Items)
            {
                if (item.ExpandSuperclasses(t))
                {
                    t.IsSelected = true;
                    break;
                }
            }

        }

        void GoToItem()
        {
            PopupControl.HorizontalOffset = 31;
            PopupControl.VerticalOffset = 49;
            PopupControl.IsOpen = true;
            ReturnConditions(txtCity.Text);
        }
#endregion

#region Textbox Events

        private void txtCity_GotFocus(object sender, RoutedEventArgs e)
        {
            IsTextboxFocus = true;
        }

        private void txtCity_LostFocus(object sender, RoutedEventArgs e)
        {
            CheckFocus();
            IsTextboxFocus = false;
        }

        private void TextBox_TextChanged(object sender, TextChangedEventArgs e)
        {
            if (txtCity.Text == "")
            {
                HideTreeview();
            }
            else if (selectedText == false) 
            {
                GoToItem();
            }
        }

        private void txtCity_KeyUp(object sender, KeyEventArgs e)
        {
            
            if (e.Key == Key.Enter && SelectedClass != null)
            {
                txtCity.Text = SelectedClass.CityName;
                selectedText = true;
                HideTreeview();
            }
            else if ((e.Key == Key.Down || e.Key == Key.Up) && tv != null)
            {
                tv.Focus();
            }
            else if (e.Key == Key.Escape)
            {
                HideTreeview();
            }
        }

        private void txtCity_KeyDown(object sender, KeyEventArgs e)
        {
            selectedText = false;
        }

        #endregion
    }    
}