Progect/TaskPage.xaml.cs

using System;
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;
using WpfApp1.Entities;

namespace WpfApp1
{
    /// <summary>
    /// Логика взаимодействия для TaskPage.xaml
    /// </summary>
    public partial class TaskPage : Page
    {
        public TaskPage()
        {
            InitializeComponent();

            LViewTasks.ItemsSource = user20Entities.GetContext().Task.ToList();

            var allTypes = user20Entities.GetContext().Task.ToList();
            allTypes.Insert(0, new WpfApp1.Entities.Task
            {
                Title = "Все типы"
            });
            ComboType.ItemsSource = allTypes;

            CheckDeleted.IsChecked = true;
            ComboType.SelectedIndex = 0;
        }


        private void TBoxSearch_TextChanged(object sender, TextChangedEventArgs e)
        {
            UpdateTasks();
        }

        private void UpdateTasks()
        {
            var searchText = TBoxSearch.Text.ToLower();
            var Tasks = user20Entities.GetContext().Task.ToList();

            var currentTasks = user20Entities.GetContext().Task.ToList();

            if (ComboType.SelectedIndex > 0)
                currentTasks = currentTasks.Where(p => p.WorkType == ComboType.SelectedItem).ToList();

            currentTasks = currentTasks.Where(p => p.Title.ToLower().Contains(TBoxSearch.Text.ToLower())).ToList();
            if (CheckDeleted.IsChecked.Value)
                currentTasks = currentTasks.Where(p => p.IsDeleted).ToList();


        }

        private void CheckDeleted_Checked(object sender, RoutedEventArgs e)
        {
            UpdateTasks();
        }

        private void ComboType_SelectionChanged(object sender, SelectionChangedEventArgs e)
        {
            UpdateTasks();
        }
    }
}