/// <summary>

    /// AutoCompleteComboBox

    /// </summary>

    public class AutoCompleteComboBox : ComboBox

    {

        #region DependencyProperty

        public string WaterMark

        {

            get { return (string)GetValue(WaterMarkProperty); }

            set { SetValue(WaterMarkProperty, value); }

        }

        // Using a DependencyProperty as the backing store for WaterMark.  This enables animation, styling, binding, etc...

        public static readonly DependencyProperty WaterMarkProperty =

            DependencyProperty.Register("WaterMark", typeof(string), typeof(AutoCompleteComboBox), new PropertyMetadata(null, new PropertyChangedCallback(OnWaterMarkChanged)));

        public bool? IsNull

        {

            get { return (bool?)GetValue(IsNullProperty); }

            set { SetValue(IsNullProperty, value); }

        }

        // Using a DependencyProperty as the backing store for IsNull.  This enables animation, styling, binding, etc...

        public static readonly DependencyProperty IsNullProperty =

            DependencyProperty.Register("IsNull", typeof(bool?), typeof(AutoCompleteComboBox), new PropertyMetadata(null));

        public bool? SetFocuse

        {

            get { return (bool?)GetValue(SetFocuseProperty); }

            set { SetValue(SetFocuseProperty, value); }

        }

        // Using a DependencyProperty as the backing store for SetFocuse.  This enables animation, styling, binding, etc...

        public static readonly DependencyProperty SetFocuseProperty =

            DependencyProperty.Register("SetFocuse", typeof(bool?), typeof(AutoCompleteComboBox), new PropertyMetadata(null, new PropertyChangedCallback(OnSetFocuseChanged)));

        public bool IsAllowNull

        {

            get { return (bool)GetValue(IsAllowNullProperty); }

            set { SetValue(IsAllowNullProperty, value); }

        }

        // Using a DependencyProperty as the backing store for IsAllowNull.  This enables animation, styling, binding, etc...

        public static readonly DependencyProperty IsAllowNullProperty =

            DependencyProperty.Register("IsAllowNull", typeof(bool), typeof(AutoCompleteComboBox), new PropertyMetadata(true, new PropertyChangedCallback(OnIsAllowNullChanged)));

        private static void OnIsAllowNullChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)

        {

        }

        #endregion

        #region Event

        private static void OnWaterMarkChanged(DependencyObject obj, DependencyPropertyChangedEventArgs e)

        {

        }

        private static void OnSetFocuseChanged(DependencyObject obj, DependencyPropertyChangedEventArgs e)

        {

            AutoCompleteComboBox wm = obj as AutoCompleteComboBox;

            if (e.NewValue != null && wm.EditableTextBox != null)

            {

                if ((bool)e.NewValue == true && wm.EditableTextBox.IsFocused != true)

                {

                    wm.EditableTextBox.Focus();

                }

            }

        }

        public IList DataSource

        {

            get { return (IList)GetValue(DataSourceProperty); }

            set { SetValue(DataSourceProperty, value); }

        }

        // Using a DependencyProperty as the backing store for DataSource.  This enables animation, styling, binding, etc...

        public static readonly DependencyProperty DataSourceProperty =

            DependencyProperty.Register("DataSource", typeof(IList), typeof(AutoCompleteComboBox), new UIPropertyMetadata(null, new PropertyChangedCallback(OnDataSourceChanged)));

        private static void OnDataSourceChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)

        {

            AutoCompleteComboBox a = d as AutoCompleteComboBox;

            //if (a.IsAllowNull)

            //{

                a.Items.Clear();

                if (a.DataSource != null)

                {

                    Type b = null;

                    foreach (var item in a.DataSource)

                    {

                        if (b == null)

                        {

                            b = item.GetType();

                            object o = Activator.CreateInstance(b);

                            //o.GetType().GetProperty(a.DisplayMemberPath).SetValue(o, "----Select----", null);

                            a.Items.Add(o);

                        }

                        a.Items.Add(item);

                    }

                }

                else

                {

                    a.ItemsSource = null;

                }

            //}

        }

        protected override void OnDropDownOpened(EventArgs e)

        {

            base.OnDropDownOpened(e);

            if (this.HasItems)

            {

                this.Items[].GetType().GetProperty(this.DisplayMemberPath).SetValue(this.Items[], "----Select----", null);

            }

        }

        protected override void OnDropDownClosed(EventArgs e)

        {

            base.OnDropDownClosed(e);

            if (this.SelectedIndex == )

            {

                //this.SelectedItem = null;

                //this.SelectedItem = null;

                //this.Text = null;

                //this.SelectedValue = null;

                this.SelectedIndex = -;

            }

        }

        public override void OnApplyTemplate()

        {

            base.OnApplyTemplate();

            //load the text box control

            if (this.EditableTextBox != null && this.MyWaterMarkTextBlock != null)

            {

                if (SetFocuse == true)

                {

                    if (!this.EditableTextBox.IsFocused)

                    {

                        this.EditableTextBox.Focus();

                    }

                }

                this.EditableTextBox.TextChanged += new TextChangedEventHandler(EditableTextBox_TextChanged);

                this.EditableTextBox.GotFocus += EditableTextBox_GotFocus;

                this.Loaded += AutoCompleteComboBox_Loaded;

            }

        }

        void AutoCompleteComboBox_Loaded(object sender, RoutedEventArgs e)

        {

            if (string.IsNullOrWhiteSpace(this.Text))

            {

                this.MyWaterMarkTextBlock.Visibility = Visibility.Visible;

                //this.MyWaterMarkTextBlock.Text = WaterMark;

                this.IsNull = false;

            }

            else

            {

                this.MyWaterMarkTextBlock.Visibility = Visibility.Collapsed;

                //this.MyWaterMarkTextBlock.Text = WaterMark;

                this.IsNull = true;

            }

            try

            {

                //if (this.HasItems)

                //{

                //    this.Items[0].GetType().GetProperty(this.DisplayMemberPath).SetValue(this.Items[0], "----Select----", null);

                //}

                //if (!this.IsAllowNull)

                //{

                //    this.EditableTextBox.IsEnabled = false;

                //}

            }

            catch (Exception)

            {

            }

        }

        void EditableTextBox_GotFocus(object sender, RoutedEventArgs e)

        {

            if (this.MyWaterMarkTextBlock.Visibility == Visibility.Visible)

            {

                // this.Text = null;

                this.MyWaterMarkTextBlock.Visibility = Visibility.Collapsed;

                //this.MyWaterMarkTextBlock.Text = WaterMark;

            }

            this.IsDropDownOpen = true;

        }

        protected override void OnSelectionChanged(SelectionChangedEventArgs e)

        {

           base.OnSelectionChanged(e);

                if (this.SelectedIndex == )

                {

                    this.SelectedIndex = -;

                } 

        }

        void EditableTextBox_TextChanged(object sender, TextChangedEventArgs e)

        {

            if (this.EditableTextBox.IsFocused && this.IsDropDownOpen == false)

            {

                this.IsDropDownOpen = true;

            }

            if (string.IsNullOrWhiteSpace(this.Text))

            {

                if (!this.EditableTextBox.IsFocused)

                {

                    this.MyWaterMarkTextBlock.Visibility = Visibility.Visible;

                    // this.MyWaterMarkTextBlock.Text = WaterMark;

                }

                this.IsNull = false;

            }

            else

            {

                this.IsNull = true;

                this.MyWaterMarkTextBlock.Visibility = Visibility.Collapsed;

                // this.MyWaterMarkTextBlock.Text = WaterMark;

            }

        }

        void SimpleAutoCompleteComboBox_LostFocus(object sender, RoutedEventArgs e)

        {

            this.IsDropDownOpen = false;

            // to prevent misunderstanding that user has entered some information

            if (this.SelectedIndex == - || this.SelectedIndex == )

            {

                this.Text = null;

                this.SelectedItem = null;

                this.SelectedValue = null;

                this.MyWaterMarkTextBlock.Visibility = Visibility.Visible;

                this.IsNull = false;

                // this.MyWaterMarkTextBlock.Text = WaterMark;

            }

            // syncronize text

            else

            {

                this.Text = this.SelectedText;

                this.IsNull = true;

            }

            // release timer resources

            try

            {

                this.EditableTextBox.CaretIndex = ;

            }

            catch { }

        }

        #endregion

        #region Construtor

        static AutoCompleteComboBox()

        {

            DefaultStyleKeyProperty.OverrideMetadata(typeof(AutoCompleteComboBox), new FrameworkPropertyMetadata(typeof(AutoCompleteComboBox)));

        }

        public AutoCompleteComboBox()

        {

            this.StaysOpenOnEdit = true;

            this.IsEditable = true;

            this.IsTextSearchEnabled = true;

            this.LostFocus += SimpleAutoCompleteComboBox_LostFocus;

            this.IsAllowNull = true;

        }

        #endregion

        protected override void OnItemsSourceChanged(System.Collections.IEnumerable oldValue, System.Collections.IEnumerable newValue)

        {

            base.OnItemsSourceChanged(oldValue, newValue);

        }

        #region property

        /// <summary>

        /// Gets the waterMark  .

        /// </summary>

        protected TextBlock MyWaterMarkTextBlock

        {

            get

            {

                return base.GetTemplateChild("PART_MyWaterMarkTextBlock") as TextBlock;

            }

        }

        /// <summary>

        /// Gets the text box in charge of the editable portion of the combo box.

        /// </summary>

        protected TextBox EditableTextBox

        {

            get

            {

                return base.GetTemplateChild("PART_EditableTextBox") as TextBox;

            }

        }

        private string SelectedText

        {

            get

            {

                try

                {

                    if (this.SelectedIndex == -) return null;

                    if (this.SelectedItem != null)

                    {

                        return this.SelectedItem.GetType().GetProperty(this.DisplayMemberPath).GetValue(this.SelectedItem, null).ToString();

                    }

                    else

                    {

                        return null;

                    }

                }

                catch (System.Exception)

                {

                    return null;

                }

            }

        }

        #endregion

    }