How to filter complete words in suggestion list using SfTextBoxExt control

<Page
x:Class="App3.MainPage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="using:App3"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:syncfusion="using:Syncfusion.UI.Xaml.Controls.Input"
mc:Ignorable="d">
<Grid Background="{StaticResource ApplicationPageBackgroundThemeBrush}">
<syncfusion:SfTextBoxExt AutoCompleteMode="Suggest" AutoCompleteSource="{Binding Stocks}"
VerticalAlignment="Center" HorizontalAlignment="Center" Width="200"
SuggestionMode="Custom"  SearchItemPath="Title" x:Name="filter"></syncfusion:SfTextBoxExt>
</Grid>
</Page>

namespace App3
{
/// <summary>
/// An empty page that can be used on its own or navigated to within a Frame.
/// </summary>
public sealed partial class MainPage : Page
{
public MainPage()
{
this.InitializeComponent();
DataContext = new ViewModel();
filter.Filter = CustomFilter;
}
private bool CustomFilter(object search, object item)
{
if ((item as Model).Title.ToLower().StartsWith(search.ToString().ToLower()))
return true;
return false;
}
 
/// <summary>
/// Invoked when this page is about to be displayed in a Frame.
/// </summary>
/// <param name="e">Event data that describes how this page was reached.  The Parameter
/// property is typically used to configure the page.</param>
protected override void OnNavigatedTo(NavigationEventArgs e)
{
}
}
public class Model
{
private string title;
public string Title
{
get { return title; }
set { title = value; }
}
}
public class ViewModel
{
private ObservableCollection<Model> stocks;
public ObservableCollection<Model> Stocks
{
get { return stocks; }
set { stocks = value; }
}
 
public ViewModel()
{
stocks = new ObservableCollection<Model>();
stocks.Add(new Model() { Title = "F" });
stocks.Add(new Model() { Title = "FB" });
stocks.Add(new Model() { Title = "FCX" });
stocks.Add(new Model() { Title = "FEYE" });
stocks.Add(new Model() { Title = "FIT" });
}
}
}