问在UI上过滤ObservableCollection项目

EN

main window XAML

<Window x:Class="UIToDoList_2.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:UIToDoList_2"
        mc:Ignorable="d"
        Title="To Do List" Height="290" Width="500" ResizeMode="CanMinimize">
    <Grid Margin="0,0,0,0">
        <StackPanel Name="MainPanel">
            <StackPanel Name="ViewTaskPanel" Margin="10">
                <StackPanel Orientation="Horizontal">
                    <TextBlock Text="Task" Margin="0,0,10,0"/>
                    <StackPanel Orientation="Vertical">
                        <ListBox x:Name="UITasks"  Width="300" Height="100" VerticalAlignment="Top" Margin="0,0,10,5"
                                 DisplayMemberPath="Name"/>
                        <RadioButton x:Name="ShowAll" Content="Show All"/>
                        <RadioButton x:Name="ShowCompleted" Content="Show Completed" />
                        <RadioButton x:Name="ShowPending" Content="Show Pending"/>
                    </StackPanel>

                    <StackPanel>
                        <Button Content="Mark As Completed" Margin="0,0,0,5"/>
                        <Button Content="Mark As Pending" Margin="0,0,0,5"/>
                        <Button x:Name="DltTaskBtn" Content="Delete Task"
                                Margin="0,0,0,5" Click="DltTaskBtn_Click"/>
                        <Button x:Name="RenameBtn" Content="Rename" Click="RenameBtn_Click"/>
                    </StackPanel>
                </StackPanel>

            </StackPanel>
            <StackPanel Name="AddTaskPanel" Margin="10">
                <TextBlock Text="Add New Task"/>
                <StackPanel Orientation="Horizontal" Margin="2">
                    <TextBlock Text="Task Name" Margin="0,0,10,0"/>
                    <TextBox Name="TaskNameTxt" Width="260"/>
                </StackPanel>
                <StackPanel Orientation="Horizontal">
                    <Button x:Name="AddTaskBtn" Content="Add" Margin="5" Click="AddTaskBtn_Click"/>
                    <Button x:Name="ClearTaskTxt" Content="Clear" Margin="5" Click="ClearTaskTxt_Click"/>
                </StackPanel>
            </StackPanel>
        </StackPanel>
    </Grid>
</Window>

public class Task : INotifyPropertyChanged
    {
        private string _Name;

        public string Name
        {
            get { return this._Name; }
            set
            {
                if (this._Name != value)
                {
                    this._Name = value;
                    this.NotifyPropertyChanged();
                }
            }
        }

        private Status _Status;

        public Status Status
        {
            get { return this._Status; }
            set
            {
                if (this._Status != value)
                {
                    this._Status = value;
                    this.NotifyPropertyChanged();
                }
            }
        }


        public event PropertyChangedEventHandler PropertyChanged;

        public void NotifyPropertyChanged([CallerMemberName] string propName = "")
        {
            if (this.PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(propName));
            }
        }
    }

    public enum Status
    {
        Pending = 0,
        Completed = 1
    }

    public class TaskSerialization
    {
        public string FileName { get; set; }

        public TaskSerialization(string fileName)
        {
            FileName = fileName;
        }

        /// <summary>
        /// Serialize the task list to XML File
        /// </summary>
        /// <param name="tasks"></param>
        public void SerializeTasks(List<Task> tasks)
        {
            StreamWriter sw = new StreamWriter(FileName);
            XmlSerializer sr = new XmlSerializer(typeof(List<Task>));
            sr.Serialize(sw, tasks);
            sw.Close();
        }

        /// <summary>
        /// Deserialize the taks list form XML file and return as ObservableCollection item
        /// </summary>
        /// <returns></returns>
        public ObservableCollection<Task> DeserializeTasks()
        {
            XmlSerializer sr = new XmlSerializer(typeof(List<Task>));
            FileStream fs = new FileStream(FileName, FileMode.Open);
            return new ObservableCollection<Task>((List<Task>)sr.Deserialize(fs));
        }
    }

namespace UIToDoList_2
{

    public partial class MainWindow : Window
    {
        private readonly string fileName = "ToDoList.xml";
        private readonly TaskSerialization taskSrlz;
        ObservableCollection<Task> tasks = new ObservableCollection<Task>();
        public MainWindow()
        {
            InitializeComponent();
            taskSrlz = new TaskSerialization(fileName);
            tasks = taskSrlz.DeserializeTasks();
            UITasks.ItemsSource = tasks;
        }

        private void AddTaskBtn_Click(object sender, RoutedEventArgs e)
        {
            AddTask();
        }
        private void DltTaskBtn_Click(object sender, RoutedEventArgs e)
        {
            DeleteTask();
        }

        private void AddTask()
        {
            var taskName = TaskNameTxt.Text;
            if (!string.IsNullOrWhiteSpace(taskName))
            {
                tasks.Add(new Task() { Name = TaskNameTxt.Text, Status = Status.Pending });
                taskSrlz.SerializeTasks(new List<Task>(tasks));
            }
            else
                MessageBox.Show("Task name cannot be null", "Error in Task name", MessageBoxButton.OK, MessageBoxImage.Error);

        }

        private void DeleteTask()
        {
            if(UITasks.SelectedItem != null)
            {
                var selectedTask = (UITasks.SelectedItem as Task);
                tasks.Remove(selectedTask);
                taskSrlz.SerializeTasks(new List<Task>(tasks));
            }
        }

        private void RenameBtn_Click(object sender, RoutedEventArgs e)
        {
            if (UITasks.SelectedItem != null)
            {
                (UITasks.SelectedItem as Task).Name = TaskNameTxt.Text;
                taskSrlz.SerializeTasks(new List<Task>(tasks));
            }
        }

        private void ClearTaskTxt_Click(object sender, RoutedEventArgs e)
        {
            TaskNameTxt.Clear();
        }
    }
}