Filter ComboBox

<Window x:Class="WpfApp1.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"

        mc:Ignorable="d"
        Title="MainWindow" SizeToContent="WidthAndHeight" PreviewKeyDown="Window_PreviewKeyDown">
    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="300"/>
            <ColumnDefinition Width="150"/>
        </Grid.ColumnDefinitions>
        <Grid.RowDefinitions>
            <RowDefinition Height="30"/>
            <RowDefinition Height="300"/>
        </Grid.RowDefinitions>

        <ComboBox Grid.Row="0" Grid.Column="0" Name="cmb1" DisplayMemberPath="Name" IsEditable="True" IsTextSearchEnabled="False" DataObject.Pasting="cmb_Pasting" PreviewKeyDown="cmb_PreviewKeyDown" PreviewTextInput="cmb_PreviewTextInput">
            <ComboBox.ItemContainerStyle>
                <Style TargetType="ComboBoxItem">
                    <EventSetter Event="PreviewMouseLeftButtonUp" Handler="ComboBoxItem_PreviewMouseLeftButtonUp"/>
                </Style>
            </ComboBox.ItemContainerStyle>
        </ComboBox>
        <ComboBox Grid.Row="0" Grid.Column="1" Name="cmb2" DisplayMemberPath="Name" IsEditable="True" IsTextSearchEnabled="False" DataObject.Pasting="cmb_Pasting" PreviewKeyDown="cmb_PreviewKeyDown" PreviewTextInput="cmb_PreviewTextInput">
            <ComboBox.ItemContainerStyle>
                <Style TargetType="ComboBoxItem">
                    <EventSetter Event="PreviewMouseLeftButtonUp" Handler="ComboBoxItem_PreviewMouseLeftButtonUp"/>
                </Style>
            </ComboBox.ItemContainerStyle>
        </ComboBox>

        <TextBox Grid.Row="1" Grid.Column="0" x:Name="info"/>
    </Grid>
</Window>






using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace WpfApp1
{
    /// <summary>
    /// Логика взаимодействия для MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        List<Person> persons;
        List<NameClass> names;
        List<StreetClass> streets;
        string currInput = string.Empty;

        public MainWindow()
        {
            InitializeComponent();

            names = new List<NameClass>
            {
                new NameClass("123", "Кацевалов Артем"),
                new NameClass("456", "Гавриленко Клим"),
                new NameClass("789", "Плаксин Владислав"),
                new NameClass("000", "Исаков Владислав"),
            };
            streets = new List<StreetClass>
            {
                new StreetClass("123", "Смирнова"),
                new StreetClass("456", "Давыдова"),
                new StreetClass("789", "Победы"),
                new StreetClass("000", "Арбат"),
            };

            persons = new List<Person>
            {
                new Person("Кацевалов Артем", "Смирнова"),
                new Person("Гавриленко Клим", "Арбат"),
                new Person("Исаков Владислав", "Давыдова"),
                new Person("Гавриленко Клим", "Смирнова"),
                new Person("Плаксин Владислав", "Давыдова"),
                new Person("Кацевалов Артем", "Победы")
            };

            cmb1.ItemsSource = names;
            cmb2.ItemsSource = streets;
            cmb1.Items.Refresh();
            cmb2.Items.Refresh();
        }

        public static T GetChildOfType<T>(DependencyObject depObj) where T : DependencyObject
        {
            if (depObj == null) return null;

            for (int i = 0; i < VisualTreeHelper.GetChildrenCount(depObj); i++)
            {
                var child = VisualTreeHelper.GetChild(depObj, i);

                var result = (child as T) ?? GetChildOfType<T>(child);
                if (result != null) return result;
            }
            return null;
        }

        private void cmb_PreviewKeyDown(object sender, KeyEventArgs e)
        {
            if (e.Key == Key.Back || e.Key == Key.Delete)
            {
                ComboBox cmb = (ComboBox)sender;

                if (!string.IsNullOrEmpty(cmb.Text) && cmb.Text.Length > 1 && cmb.Text.Length > GetChildOfType<TextBox>(cmb).SelectedText.Length)
                {
                    if (cmb == cmb1)
                        cmb.ItemsSource = names.Where(p => p.Name.IndexOf(cmb.Text, StringComparison.InvariantCultureIgnoreCase) != -1).ToList();
                    else if (cmb == cmb2)
                        cmb.ItemsSource = streets.Where(p => p.Name.IndexOf(cmb.Text, StringComparison.InvariantCultureIgnoreCase) != -1).ToList();
                    cmb.IsDropDownOpen = true;
                }
                else
                {
                    if (cmb == cmb1)
                        cmb.ItemsSource = names;
                    else if (cmb == cmb2)
                        cmb.ItemsSource = streets;
                    cmb.IsDropDownOpen = false;
                    cmb.SelectedItem = null;
                }
                //cmb.Focus();
            }
        }

        private void FilterRequest()
        {
            Person per;
            try
            {
                per = persons.Where(p => p.Name.Equals((cmb1.SelectedItem as NameClass)?.Name) && p.Street == (cmb2.SelectedItem as StreetClass)?.Name).ToList()[0];
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
                info.Clear();
                return;
            }
            info.Text = $"\n\n\n\n\nName: {per?.Name}\nStreet: {per?.Street}";
        }

        private void cmb_PreviewTextInput(object sender, TextCompositionEventArgs e)
        {
            ComboBox cmb = (ComboBox)sender;

            cmb.IsDropDownOpen = true;

            if (!string.IsNullOrEmpty(cmb.Text) && !(GetChildOfType<TextBox>(cmb).SelectedText.Length == cmb.Text.Length))
            {
                if (cmb == cmb1)
                    cmb.ItemsSource = names.Where(p => p.Name.IndexOf(cmb.Text, StringComparison.InvariantCultureIgnoreCase) != -1).ToList();
                else if (cmb == cmb2)
                    cmb.ItemsSource = streets.Where(p => p.Name.IndexOf(cmb.Text, StringComparison.InvariantCultureIgnoreCase) != -1).ToList();
                cmb.IsDropDownOpen = true;

                currInput = cmb.Text.Insert(GetChildOfType<TextBox>(cmb).CaretIndex, e.Text);
            }
            else if (!string.IsNullOrEmpty(e.Text))
            {
                if (cmb == cmb1)
                    cmb.ItemsSource = names.Where(p => p.Name.IndexOf(e.Text, StringComparison.InvariantCultureIgnoreCase) != -1).ToList();
                else if (cmb == cmb2)
                    cmb.ItemsSource = streets.Where(p => p.Name.IndexOf(e.Text, StringComparison.InvariantCultureIgnoreCase) != -1).ToList();
            }
            else
            {
                if (cmb == cmb1)
                    cmb.ItemsSource = names;
                else if (cmb == cmb2)
                    cmb.ItemsSource = streets;
            }
        }

        private void cmb_Pasting(object sender, DataObjectPastingEventArgs e)
        {
            ComboBox cmb = (ComboBox)sender;

            cmb.IsDropDownOpen = true;

            string pastedText = (string)e.DataObject.GetData(typeof(string));
            currInput = cmb.Text.Insert(GetChildOfType<TextBox>(cmb).CaretIndex, pastedText);

            if (!string.IsNullOrEmpty(currInput))
            {
                if (cmb == cmb1)
                    cmb.ItemsSource = names.Where(p => p.Name.IndexOf(currInput, StringComparison.InvariantCultureIgnoreCase) != -1).ToList();
                else if (cmb == cmb2)
                    cmb.ItemsSource = streets.Where(p => p.Name.IndexOf(currInput, StringComparison.InvariantCultureIgnoreCase) != -1).ToList();
            }
            else
            {
                if (cmb == cmb1)
                    cmb.ItemsSource = names;
                else if (cmb == cmb2)
                    cmb.ItemsSource = streets;
            }
        }

        private void Window_PreviewKeyDown(object sender, KeyEventArgs e)
        {
            if ((e.Key == Key.Down || e.Key == Key.Up) && e.Source is ComboBox)
            {
                (e.Source as ComboBox).IsDropDownOpen = true;
            }
            else if ((e.Key == Key.Enter || e.Key == Key.Return) && e.Source is ComboBox)
            {
                if ((e.Source as ComboBox).SelectedItem == null) return;
                currInput = (e.Source as ComboBox).Text;
                FilterRequest();
            }
        }

        private void ComboBoxItem_PreviewMouseLeftButtonUp(object sender, MouseButtonEventArgs e)
        {
            if ((sender as ComboBoxItem).DataContext is NameClass)
            {
                cmb1.SelectedItem = names.Where(p => p.ID == ((sender as ComboBoxItem).DataContext as NameClass)?.ID).ToList()[0];
                currInput = cmb1.Text;
            }
            else if ((sender as ComboBoxItem).DataContext is StreetClass)
            {
                cmb2.SelectedItem = streets.Where(a => a.ID == ((sender as ComboBoxItem).DataContext as StreetClass)?.ID).ToList()[0];
                currInput = cmb2.Text;
            }
            FilterRequest();
        }
    }

    public class Person
    {

        public string Name { get; set; }
        public string Street { get; set; }

        public Person(string n, string s) { Name = n; Street = s; }
    }

    public class NameClass
    {
        public string ID { get; set; }
        public string Name { get; set; }

        public NameClass(string i, string n) { ID = i; Name = n; }
    }

    public class StreetClass
    {
        public string ID { get; set; }
        public string Name { get; set; }

        public StreetClass(string i, string n) { ID = i; Name = n; }
    }
}