Prefix Characters Constraint in WPF Autocomplete (SfTextBoxExt)

Instead of displaying suggestion list on every character entry, matches can be filtered and displayed after a few character entries. This can be done using the MinimumPrefixCharacter` property, and their default value is 1.

xaml

<Window x:Class="AutoCompleteSample.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:AutoCompleteSample"
        mc:Ignorable="d"
        xmlns:editors="clr-namespace:Syncfusion.Windows.Controls.Input;assembly=Syncfusion.SfInput.Wpf"
        Title="MainWindow" Height="450" Width="800">
    <Window.Content>
        <Grid>
            <editors:SfTextBoxExt x:Name="textBoxExt" 
                              HorizontalAlignment="Center" 
                              VerticalAlignment="Center" 
                              AutoCompleteMode="Suggest"
                              MinimumPrefixCharacters="2"
                              Width="300"/>
        </Grid>
    </Window.Content>
</Window>

c#

using Syncfusion.Windows.Controls.Input;
using System.Collections.Generic;
using System.Windows;

namespace AutoCompleteSample
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
            SfTextBoxExt textBoxExt = new SfTextBoxExt()
            {
                HorizontalAlignment = HorizontalAlignment.Center,
                VerticalAlignment = VerticalAlignment.Center,
                Width = 200,
                AutoCompleteMode = AutoCompleteMode.Suggest,
                MinimumPrefixCharacters = 2
            };

            List<string> list = new List<string>()
            {
                 "India",
                 "Uganda",
                 "Ukraine",
                 "Canada",
                 "United Arab Emirates"
            };

            textBoxExt.AutoCompleteSource = list;
            this.Content = textBoxExt;
        }
    }
}

Minimum Prefix Length case