【转载】wpf数据绑定binding与INotifyPropertyChanged

WPF数据绑定号称是：数据变化会通过界面更新数据，这对新手而言，绝对是个误区，在我听说这句话的时候，我真是高兴，用了以后才发现其实没有那么美。要实现前面号称的特性，需要三个条件：1、进行绑定，2、绑定的来源要实现INotifyPropertyChanged接口，意思是，源改变了要去通知目标。3、目标要是依赖属性。
下面简单贴个例子。
XAML文件：

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<Window x:Class="InotifyChangedTest.Window1"
   xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
   xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
       xmlns:local ="clr-namespace:InotifyChangedTest"
   Title="Window1" Height="300" Width="300">
    <Grid>
        <TextBox Height="23" Margin="40,43,52,0" Name="textBox1" VerticalAlignment="Top" Text="{Binding Path=name}"/>
        <TextBox Height="23" Margin="40,94,52,0" Name="textBox2" VerticalAlignment="Top" Text="{Binding Path=desc}"/>
        <Button Height="23" Margin="106,0,97,42" Name="button1" VerticalAlignment="Bottom" Click="button1_Click">Button</Button>
    </Grid>
</Window>

TextBox 的Text是依赖属性。

cs文件，新手问题一般都比较多，我就把所有代码都复制过来了：

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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;
using System.ComponentModel;

namespace InotifyChangedTest
{
    /// <summary>
    /// Interaction logic for Window1.xaml
    /// </summary>
    public partial class Window1 : Window
    {
        public person ps{get;set;}
        public Window1()
        {
            InitializeComponent();
            ps = new person();
            //注意这句，指定数据源
            this.DataContext = ps;
        }

        private void button1_Click(object sender, RoutedEventArgs e)
        {
            ps.name += "a";
            ps.desc += "b";
        }

    }
//实现INotifyPropertyChanged接口，当数据改变时通知
    public class person:INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;
        private string _name;
        public string name
        {
            get
            {
                return _name;
            }
            set
            {
                if (value != _name)
                {
                    _name = value;
                    //改变时通知
                    prochanged("name");
                }
            }
        }
        private string _desc;
        public string desc
        {
            get
            {
                return _desc;
            }
            set
            {
                if (value != _desc)
                {
                    _desc = value;
                    //改变时进行通知
                    prochanged("desc");
                }
            }
        }
       
        private void prochanged(string info)
        {
            if (PropertyChanged != null)
            {
                //是不是很奇怪，这个事件发起后，处理函数在哪里？
                //我也不知道在哪里，我只知道，绑定成功后WPF会帮我们决定怎么处理。
                PropertyChanged(this, new PropertyChangedEventArgs(info));
            }
        }
    }
}

前面的数源是在代码里通过this.DataContext = ps;这句话绑定的。接下来，贴两段代码，用XAML来替代这句话。

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<Window x:Class="InotifyChangedTest.Window1"
   xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
   xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
   xmlns:local ="clr-namespace:InotifyChangedTest"
   Title="Window1" Height="300" Width="300">
    <Window.Resources>
        <local:personContainer x:Key="myDataSource" />
    </Window.Resources>
    <Grid>
        <TextBox Height="23" Margin="40,43,52,0" Name="textBox1" VerticalAlignment="Top" Text="{Binding Path=ps.name,Source={StaticResource myDataSource}}"/>
        <TextBox Height="23" Margin="40,94,52,0" Name="textBox2" VerticalAlignment="Top" Text="{Binding Path=ps.desc,Source={StaticResource myDataSource}}"/>
        <Button Height="23" Margin="106,0,97,42" Name="button1" VerticalAlignment="Bottom" Click="button1_Click">Button</Button>
    </Grid>
</Window>

注意上面，定义了一个资源，程序的编译的时候会自动创建这个资源的实例。

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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;
using System.ComponentModel;

namespace InotifyChangedTest
{
    /// <summary>
    /// Interaction logic for Window1.xaml
    /// </summary>
    public partial class Window1 : Window
    {
        public personContainer pc;
        public Window1()
        {
            InitializeComponent();
            //这里为什么不用下面注释掉的这句，而用FindResource呢？
            //如果用了注释的这句，那么程序编译的时候，会新建一个personContainer实例，xaml的资源也会新建实例
            //两个实例不相同，所以就算绑定了数据，pc改变时，界面也不能更新
            //因而需要用FindResource保证XAML和CS文件使用的是同一个实例。
            //pc = new personContainer();
            pc = (personContainer)this.FindResource("myDataSource");
        }
        private void button1_Click(object sender, RoutedEventArgs e)
        {
            pc.ps.name += "a";
            pc.ps.desc += "b";
        }

    }
    public class personContainer
    {
        public person ps { get; set; }
        public personContainer()
        {
            ps = new person();
            ps.name = "ab";
            ps.desc = "dd";
        }
    }
    public class person:INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;
        private string _name;
        public string name
        {
            get
            {
                return _name;
            }
            set
            {
                if (value != _name)
                {
                    _name = value;
                    prochanged("name");
                }
            }
        }
        private string _desc;
        public string desc
        {
            get
            {
                return _desc;
            }
            set
            {
                if (value != _desc)
                {
                    _desc = value;
                    prochanged("desc");
                }
            }
        }
        private void prochanged(string info)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(info));
            }
        }
    }
}

注意到前后两个CS文件，在后面的CS里新建了一个类用来绑定，你会不会奇怪，为什么不像第一个例子一样，直接用WINDOW1里的PS呢，原因还是前面提到的，XAML里会对资源创建实例，所以如用把WINDOW1做为资源，XAML就会去创建WINDOW1的实例，CS也创建WINDOW,两个窗口冲突，编译不能通过。

posted @ 2012-03-29 16:50  火腿骑士  阅读(395)  评论(0)  编辑  收藏  举报