WPF中INotifyPropertyChanged用法与数据绑定

在WPF中进行数据绑定的时候常常会用到INotifyPropertyChanged接口来进行实现，下面来看一个INotifyPropertyChanged的案例。

下面定义一个Person类：

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

namespace WpfApp
{
public class Person:INotifyPropertyChanged
{
private String _name = "张三";
private int _age = 24;
private String _hobby = "篮球";

public String Name
{
set
{
_name = value;
if (PropertyChanged != null)//有改变
{
PropertyChanged(this, new PropertyChangedEventArgs("Name"));//对Name进行监听
}
}
get
{
return _name;
}
}

public int Age
{
set
{
_age = value;
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs("Age"));//对Age进行监听
}
}
get
{
return _age;
}
}
public String Hobby//没有对Hobby进行监听
{
get { return _hobby; }
set { _hobby = value; }
}
public event PropertyChangedEventHandler PropertyChanged;
}
}

上面定义的这个Person类中，对Name和Age属性进行了监听，但是没有对Hobby进行监听。

MainWindow.xmal界面文件定义的内容如下：

<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="显示用户信息" Height="26" HorizontalAlignment="Left" Margin="60,118,0,0" Name="button1" VerticalAlignment="Top" Width="144" Click="button1_Click" />
<Button Content="修改用户信息" 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>

后台代码是：

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 的交互逻辑
/// </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;//绑定数据
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";
}
}
}

当点击显示用户数据的时候



下面看看这些信息具体都来自于哪儿？



由于在Person中没有对Hobby进行监听，所以p1.Hobby="足球"这个语句没有起到作用。 点击修改用户信息的时候也是不能修改绑定到界面上的对应Hobby的信息（即使是在界面处写了Mode=TwoWay,也是不能进行绑定的）。

所以使用INotifyPropertyChanged的时候，需要对要进行绑定的属性进行显示的设置的，否则绑定的时候是不能进行双向绑定的,即绑定是无效的。