WPF AutoComplete TextBox

default:
    SelectorControl.SelectedIndex = 0;
    break;

HandleKeyDown(KeyEventArgs key)

<wpf:AutoCompleteTextBox Provider="{Binding Test}" x:Name="name" RenderTransformOrigin="0.487,1.558" Height="26" VerticalAlignment="Bottom" Margin="2,0,224,28" Grid.RowSpan="2" Grid.ColumnSpan="3"/>

public class Test : ISuggestionProvider
    {

        public System.Collections.IEnumerable GetSuggestions(string filter)
        {
            List<string> nameList = new List<string>
            {
                "9599904947","9999678444"
            };

            if (string.IsNullOrEmpty(filter))
            {
                return null;
            }
            if (filter.Length < 2)
            {
                return null;
            }

            if (filter[1] != ':')
            {
                return null;
            }

            List<string> autoList = new List<string>();
            autoList.Clear();

            foreach (string item in nameList)
            {
                if (!string.IsNullOrEmpty(filter))
                {
                    if (item.StartsWith(filter))
                    {
                        autoList.Add(item);
                    }
                }
            }

           return nameList;
        }

private void OnEditorKeyDown(object sender, KeyEventArgs e)
 {
   if (SelectionAdapter != null)
   {
     if (IsDropDownOpen)
       SelectionAdapter.HandleKeyDown(e);
     else
       IsDropDownOpen = e.Key == Key.Down || e.Key == Key.Up;
   }
   this.Text = this.Editor.Text;  // Save to Text Property
 }

public static void OnSelectedItemChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
  AutoCompleteTextBox act = null;
  act = d as AutoCompleteTextBox;
  if (act != null)
  {
    if (act.Editor != null & !act._isUpdatingText)
    {
      act._isUpdatingText = true;
      if (!string.IsNullOrWhiteSpace((string)e.NewValue)) // Update if not null or string.empty
      {
        act.Editor.Text = act.BindingEvaluator.Evaluate(e.NewValue);
        act.Text = act.Editor.Text;
      }
      act._isUpdatingText = false;
    }
  }
}

If Editor.Text.Length > 0 Then
            IsLoading = True    
            IsDropDownOpen = True       
            ItemsSelector.ItemsSource = Nothing
            FetchTimer.IsEnabled = True
            FetchTimer.Start()
        Else
            IsDropDownOpen = False
        End If

If Editor.Text.Length > 0 Then
            IsLoading = True
            If Editor.IsFocused Then
                IsDropDownOpen = True
            End If
            ItemsSelector.ItemsSource = Nothing
            FetchTimer.IsEnabled = True
            FetchTimer.Start()
        Else
            IsDropDownOpen = False
        End If

<wpfControls:AutoCompleteTextBox Text="{Binding Supplier, Mode=TwoWay}" Style="{StaticResource AutoBoxStyle}" Provider="{StaticResource ResourceKey=SupplierProvider}" SelectedItem="{Binding RelativeSource={RelativeSource Self}, Path=Text}"></wpfControls:AutoCompleteTextBox>