WPF中INotifyPropertyChanged用法與數據綁定

在WPF中進行數據綁定的時候常常會用到INotifyPropertyChanged接口來進行實現，下面來看一個INotifyPropertyChanged的案例。

下面定義一個Person類：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.ComponentModel;

namespace WpfApp
{
    public class Person:INotifyPropertyChanged
    {
        private String _name = "張三";
        private int _age = 24;
        private String _hobby = "籃球";

        public String Name
        {
            set
            {
                _name = value;
                if (PropertyChanged != null)//有改變
                {
                    PropertyChanged(this, new PropertyChangedEventArgs("Name"));//對Name進行監聽
                }
            }
            get
            {
                return _name;
            }
        }

        public int Age
        {
            set
            {
                _age = value;
                if (PropertyChanged != null)
                {
                    PropertyChanged(this, new PropertyChangedEventArgs("Age"));//對Age進行監聽
                }
            }
            get
            {
                return _age;
            }
        }
        public String Hobby//沒有對Hobby進行監聽
        {
            get { return _hobby; }
            set { _hobby = value; }
        }
        public event PropertyChangedEventHandler PropertyChanged;
    }
}

上面定義的這個Person類中，對Name和Age屬性進行了監聽，但是沒有對Hobby進行監聽。

MainWindow.xmal界面文件定義的內容如下：

<Window x:Class="WpfApp.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="300" Width="350">
    <Grid Name="grid">
        <TextBox Height="20" Text="{Binding Path=Name}"  HorizontalAlignment="Left" Margin="63,12,0,0" Name="textBox1" VerticalAlignment="Top" Width="139" />
        <TextBox Height="20"  Text="{Binding Path=Age}"  HorizontalAlignment="Left" Margin="63,48,0,0" Name="textBox2" VerticalAlignment="Top" Width="139" />
        <TextBox Height="20" Text="{Binding Path=Hobby}"  HorizontalAlignment="Left" Margin="63,82,0,0" Name="textBox3" VerticalAlignment="Top" Width="139" />

        <Button Content="顯示用戶信息" Height="26" HorizontalAlignment="Left" Margin="60,118,0,0" Name="button1" VerticalAlignment="Top" Width="144" Click="button1_Click" />
        <Button Content="修改用戶信息" Height="26" HorizontalAlignment="Left" Margin="60,158,0,0" Name="button2" VerticalAlignment="Top" Width="144" Click="button2_Click" />

        <TextBlock Height="40" HorizontalAlignment="Left" Margin="13,201,0,0" Name="textBlock1"   Text="{Binding Path=Name}"  VerticalAlignment="Top" Width="88" />
        <TextBlock Height="40" HorizontalAlignment="Left" Margin="118,201,0,0" Name="textBlock2" Text="{Binding Path=Age}" VerticalAlignment="Top" Width="88" />
        <TextBlock Height="40" HorizontalAlignment="Left" Margin="222,201,0,0" Name="textBlock3" Text="{Binding Path=Hobby, Mode=TwoWay}" VerticalAlignment="Top" Width="88" />
    </Grid>
</Window>

後臺代碼是：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
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 WpfApp
{
    /// <summary>
    /// MainWindow.xaml 的交互邏輯
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }

        private Person p1 = new Person();
        private void button1_Click(object sender, RoutedEventArgs e)
        {
            grid.DataContext = p1;//綁定數據
            p1.Name = "李四";

            p1.Hobby = "足球";
        }
        private void button2_Click(object sender, RoutedEventArgs e)
        {
            p1.Age = p1.Age + 1;
            p1.Hobby = "足球";
        }
    }
}

當點擊顯示用戶數據的時候

下面看看這些信息具體都來自於哪兒？

由於在Person中沒有對Hobby進行監聽，所以p1.Hobby="足球"這個語句沒有起到作用。 點擊修改用戶信息的時候也是不能修改綁定到界面上的對應Hobby的信息（即使是在界面處寫了Mode=TwoWay,也是不能進行綁定的）。

所以使用INotifyPropertyChanged的時候，需要對要進行綁定的屬性進行顯示的設置的，否則綁定的時候是不能進行雙向綁定的,即綁定是無效的。