Autocomplete ComboBox WPF with 10 item history

//Will redo in MVVM later, but the quick and dirty method
//Autocomplete with filtering added
//Fixed issue with duplicate and empty history items

// In View.xaml:
<ComboBox Name="NovellHistory" HorizontalAlignment="Left" Margin="50,28,0,0" VerticalAlignment="Top" Width="200" IsEditable="True">
            <ComboBox.Style>
                <Style>
                    <EventSetter Event="TextBox.TextChanged" Handler="History_TextChanged" />
                </Style>
            </ComboBox.Style>
        </ComboBox>


// In View.cs:
public NovellDesktopView()
        {
            InitializeComponent();
            NovellHistory.ItemsSource = Settings.NovellHistory;
        }

        private void Run_Click(object sender, RoutedEventArgs e)
        {
            var history = Settings.NovellHistory;
            Settings.NovellHistory = AddHistoryItem(history, NovellHistory.Text);
        }

        private List<string> AddHistoryItem(List<string> input, string item)
        {
            var output = new List<string>();
            if (!input.Contains(item) && item.Length > 0)
                output.Add(item);
            output.AddRange(input);
            if (output.Count >= 10)
                output.RemoveAt(9);
            return output;
        }

        private void History_TextChanged(object sender, TextChangedEventArgs e)
        {
            var box = (ComboBox)sender;
            box.ItemsSource = from entry in Settings.NovellHistory where entry.ToLower().Contains(box.Text.ToLower()) select entry;
            box.IsDropDownOpen = true;
        }

//In Settings.Designer.cs
        [global::System.Configuration.UserScopedSettingAttribute()]
        [global::System.Diagnostics.DebuggerNonUserCodeAttribute()]
        [global::System.Configuration.DefaultSettingValueAttribute("")]
        public System.Collections.Generic.List<string> NovellHistory
        {
            get {
                return ((System.Collections.Generic.List<string>)(this["NovellHistory"]));
            }
            set {
                this["NovellHistory"] = value;
            }
        }

//In my Settings.cs class (because I hate typing out Properties.Settings.Default.SomeSetting)
        public static List<string> NovellHistory
        {
            get { return Properties.Settings.Default.NovellHistory; }
            set { Properties.Settings.Default.NovellHistory = value; Properties.Settings.Default.Save(); }
        }