WPF 中双向绑定通知机制

INotifyPropertyChanged实现

INotifyPropertyChanged会向客户端发出某一属性值已更改的通知。当元素属性值改变时，会通知后台model
前台代码不变，我们让后台Students Model实现INotifyPropertyChanged接口。
通过DataContext实现数据数据项的变更通知。添加一个ViewModel类，实现INotifyPropertyChanged接口

前台xmal

<Window x:Class="WpfAppTest.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" Height="450" Width="800">
    <Grid>
        <StackPanel Height="295" Width="427" HorizontalAlignment="Left" VerticalAlignment="Top" Margin="10,10,0,0" Name="stackPane1"  >
            <TextBlock Height="23" Name="txtBlock1" Text="学员编号"></TextBlock>
            <TextBox Height="23" Name="txtStudentId" Width="301" HorizontalAlignment="Left"></TextBox>
            <TextBlock Height="23" Name="txtBlock2" Text="学员列表"></TextBlock>
            <ListBox Height="156" Name="lbStudent" Width="305" HorizontalAlignment="Left" ItemsSource="{Binding StudentList,Mode=TwoWay}">
                <ListBox.ItemTemplate>
                    <DataTemplate>
                        <StackPanel Name="stackPanel2" Orientation="Horizontal">
                            <TextBlock Text="{Binding Id,Mode=TwoWay}" Margin="5" Background="Beige"></TextBlock>
                            <TextBlock Text="{Binding Name,Mode=TwoWay}" Margin="5"></TextBlock>
                            <TextBlock Text="{Binding Age,Mode=TwoWay}" Margin="5"></TextBlock>
                        </StackPanel>
                    </DataTemplate>
                </ListBox.ItemTemplate>
            </ListBox>
            <Button Content="Button" Height="23" Name="button1" Width="75" HorizontalAlignment="Left" Click="Button1_Click"></Button>
        </StackPanel>
    </Grid>
</Window>

后台cs

using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
/// <summary>
/// - 字段或属性实现INotifyPropertyChanged接口，实现了该接口，只要字段或属性的发生了改变，就会提供通知机制
/// - WPF 提供 ObservableCollection<T> 类，它是实现 INotifyCollectionChanged 接口的数据集合的内置实现，以便集合中的插入或删除操作可以自动更新 UI
/// </summary>
namespace WpfAppTest
{
    /// <summary>
    /// MainWindow.xaml 的交互逻辑
    /// </summary>
    public partial class MainWindow : Window
    {
        ViewModel viewModel = new ViewModel();

        public MainWindow()
        {
            InitializeComponent();
            viewModel.StudentList = new ObservableCollection<Students>
            {
                 new Students(){Id=1,Age=11,Name="Tom"},
                 new Students(){Id=2,Age=12,Name="Darren"},
                 new Students(){Id=3,Age=13,Name="Jacky"},
                 new Students(){Id=4,Age=14,Name="Andy"}
            };
            this.lbStudent.DataContext = viewModel;
            this.txtStudentId.SetBinding(TextBox.TextProperty, new Binding("SelectedItem.Id") { Source = lbStudent });
        }

        private void Button1_Click(object sender, RoutedEventArgs e)
        {
            viewModel.StudentList[1] = new Students() { Id = 4, Age = 14, Name = "这是一个集合改变" };
            
            viewModel.StudentList = new ObservableCollection<Students>() {
            new Students(){ Id=1, Age=11, Name="这是改变后的集合"},
            new Students(){ Id=2, Age=12, Name="这是改变后的集合"},
            new Students(){ Id=3, Age=13, Name="这是改变后的集合"},
            new Students(){ Id=4, Age=14, Name="这是改变后的集合"}
            };
            viewModel.StudentList[2].Name = "这是一个属性改变";
        }

        public class Students:INotifyPropertyChanged
        {
            public int Id { get; set; }
            string _name;
            public string Name
            {
                get { return _name; }
                set
                {
                    _name = value;
                    OnPropertyChanged("Name");
                }
            }
            public int Age { get; set; }
            protected virtual void OnPropertyChanged(string propertyName)
            {
                if (PropertyChanged != null)
                {
                    PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
                }
            }
            public event PropertyChangedEventHandler PropertyChanged;
        }

        public class ViewModel : INotifyPropertyChanged
        {
            private ObservableCollection<Students> studentList;
            public ObservableCollection<Students> StudentList {
                get { return studentList; }
                set
                {
                    if (this.studentList != value)
                    {
                        this.studentList = value;
                        OnPropertyChanged("StudentList");
                    }
                }
            }
            public event PropertyChangedEventHandler PropertyChanged;
            private void OnPropertyChanged(string propertyName)
            {
                PropertyChangedEventHandler handler = this.PropertyChanged;
                if (handler != null)
                {
                    handler(this, new PropertyChangedEventArgs(propertyName));
                }
            }
        }
    }
}