Silverlight中OneTime,OneWay,TwoWay及INotifyPropertyChanged 接口的理解

           今天有时间把Silverlight中OneTime,OneWay,TwoWay及INotifyPropertyChanged 接口的理解等数据绑定方面的东西理解学习了下！下面是我的笔记。

（一）前台代码：

<Grid x:Name="LayoutRoot" <a href="http://code.js-code.com/tag/BAC/" target="_blank" class="keywords">BAC</a>kground="White"> <StackPanel> <StackPanel Orientation="Horizontal" HorizontalAlignment="Center"> <TextBlock Height="23" Name="textBlock1" Text="编号" Width="34" /> <Text<a href="http://code.js-code.com/tag/Box/" target="_blank" class="keywords">Box</a> Text="<a href="http://code.js-code.com/tag/B/" target="_blank" class="keywords">{B</a>inding ID,Mode=OneTim<a href="http://code.js-code.com/tag/E/" target="_blank" class="keywords">E}</a>" Name="tbxID" Width="106" Height="27" ></Text<a href="http://code.js-code.com/tag/Box/" target="_blank" class="keywords">Box</a>> </StackPanel> <StackPanel Orientation="Horizontal" HorizontalAlignment="Center"> <TextBlock Height="23" Name="textBlock2" Text="书名：" /> <Text<a href="http://code.js-code.com/tag/Box/" target="_blank" class="keywords">Box</a> Text="<a href="http://code.js-code.com/tag/B/" target="_blank" class="keywords">{B</a>inding <a href="http://code.js-code.com/tag/titl/" target="_blank" class="keywords">titl</a>e,Mode=OneWay}" Name="tbx<a href="http://code.js-code.com/tag/titl/" target="_blank" class="keywords">titl</a>e" Width="108" Height="27" ></Text<a href="http://code.js-code.com/tag/Box/" target="_blank" class="keywords">Box</a>> </StackPanel> <StackPanel Orientation="Horizontal" HorizontalAlignment="Center"> <TextBlock Height="23" Name="textBlock3" Text="价格：" VerticalAlignment="Top" /> <Text<a href="http://code.js-code.com/tag/Box/" target="_blank" class="keywords">Box</a> Text="<a href="http://code.js-code.com/tag/B/" target="_blank" class="keywords">{B</a>inding Price,Mode=TwoWay}" Name="tbxPrice" Width="108" Height="27"></Text<a href="http://code.js-code.com/tag/Box/" target="_blank" class="keywords">Box</a>> </StackPanel> <StackPanel> <Button Name="MyButton" Content="通过数据源<a href="http://code.js-code.com/tag/xiugai/" target="_blank" class="keywords">修改</a>控件的值" Click="MyButton_Click" Width="140" Height="27"></Button> <Button Content="直接<a href="http://code.js-code.com/tag/xiugai/" target="_blank" class="keywords">修改</a>控件的值" Height="23" Name="button1" Width="139" Click="button1_Click" /> <Button Content="通过控件<a href="http://code.js-code.com/tag/xiugai/" target="_blank" class="keywords">修改</a>数据源的值" Height="23" Name="button2" Width="140" Click="button2_Click" /> </StackPanel> </StackPanel> </Grid>

（二）后台代码

public partial class MainPage : UserControl <a href="http://code.js-code.com/tag/" target="_blank" class="keywords">{</a> Book book = new Book(<a href="http://code.js-code.com/tag/" target="_blank" class="keywords">);</a> public MainPage() <a href="http://code.js-code.com/tag/" target="_blank" class="keywords">{</a> InitializeComponent(<a href="http://code.js-code.com/tag/" target="_blank" class="keywords">);</a> book.ID = 0; book.<a href="http://code.js-code.com/tag/titl/" target="_blank" class="keywords">titl</a>e = "ASP.NET 开发手册"; book.Price = 40; tbxID.DataCo<a href="http://code.js-code.com/tag/ntex/" target="_blank" class="keywords">ntex</a>t = book; tbx<a href="http://code.js-code.com/tag/titl/" target="_blank" class="keywords">titl</a>e.DataCo<a href="http://code.js-code.com/tag/ntex/" target="_blank" class="keywords">ntex</a>t = book; tbxPrice.DataCo<a href="http://code.js-code.com/tag/ntex/" target="_blank" class="keywords">ntex</a>t = book; } //通过<a href="http://code.js-code.com/tag/xiugai/" target="_blank" class="keywords">修改</a>数据源<a href="http://code.js-code.com/tag/xiugai/" target="_blank" class="keywords">修改</a>控件的值 //如果在没有实现INotifyPropertyChanged接口情况下，OneTime,TwoWay三种方式都不能实现数据源更改控件<a href="http://code.js-code.com/tag/zhide/" target="_blank" class="keywords">值的</a>场景 //当实现了INotifyPropertyChanged接口情况下,TwoWay能实现数据源更改控件<a href="http://code.js-code.com/tag/zhide/" target="_blank" class="keywords">值的</a>场景,而OneTime是不能实现的 //因为OneTime是初始化绑定后，控件和数据源就没关系了的 //结论：数据源--》控件 的更改就只能用OneWay,TwoWay并且需要实现INotifyPropertyChanged接口 private void MyButton_Click(ob<a href="http://code.js-code.com/tag/je/" target="_blank" class="keywords">je</a>ct sender,RoutedEventArgs <a href="http://code.js-code.com/tag/E/" target="_blank" class="keywords">E)</a> <a href="http://code.js-code.com/tag/" target="_blank" class="keywords">{</a> book.ID = 100; book.Price = 50; book.<a href="http://code.js-code.com/tag/titl/" target="_blank" class="keywords">titl</a>e = "SL开发手册"; } //通过控件<a href="http://code.js-code.com/tag/xiugai/" target="_blank" class="keywords">修改</a>数据源的值 //因为ID是OneTime,<a href="http://code.js-code.com/tag/titl/" target="_blank" class="keywords">titl</a>e用的是OneWay无论Book是否继承了INotifyPropertyChanged接口，都无法通过<a href="http://code.js-code.com/tag/xiugai/" target="_blank" class="keywords">修改</a>控件tbxID,tbx<a href="http://code.js-code.com/tag/titl/" target="_blank" class="keywords">titl</a>e的值来<a href="http://code.js-code.com/tag/xiugai/" target="_blank" class="keywords">修改</a>数据源的<a href="http://code.js-code.com/tag/zhide/" target="_blank" class="keywords">值的</a> //对于Pirce使用了TwoWay方式，无论Book是否继承了INotifyPropertyChanged接口，都可以通过<a href="http://code.js-code.com/tag/xiugai/" target="_blank" class="keywords">修改</a>tbxPrice的值<a href="http://code.js-code.com/tag/xiugai/" target="_blank" class="keywords">修改</a>数据源的值 //因为当目标和源有<a href="http://code.js-code.com/tag/yige/" target="_blank" class="keywords">一个</a>发生变化时，TwoWay 绑定既更新目标也更新源 //结论：控件---》数据源，只有使用TwoWay方式才可以<a href="http://code.js-code.com/tag/xiugai/" target="_blank" class="keywords">修改</a>数据源（且不需要实现INotifyPropertyChanged接口） private void button2_Click(ob<a href="http://code.js-code.com/tag/je/" target="_blank" class="keywords">je</a>ct sender,RoutedEventArgs <a href="http://code.js-code.com/tag/E/" target="_blank" class="keywords">E)</a> <a href="http://code.js-code.com/tag/" target="_blank" class="keywords">{</a> <a href="http://code.js-code.com/tag/messa/" target="_blank" class="keywords">messa</a>ge<a href="http://code.js-code.com/tag/Box/" target="_blank" class="keywords">Box</a>.Show(book.ID.To<a href="http://code.js-code.com/tag/Stri/" target="_blank" class="keywords">Stri</a>ng() + " " + book.<a href="http://code.js-code.com/tag/titl/" target="_blank" class="keywords">titl</a>e.To<a href="http://code.js-code.com/tag/Stri/" target="_blank" class="keywords">Stri</a>ng() + " " + book.Price.To<a href="http://code.js-code.com/tag/Stri/" target="_blank" class="keywords">Stri</a>ng()<a href="http://code.js-code.com/tag/" target="_blank" class="keywords">);</a> } //直接<a href="http://code.js-code.com/tag/xiugai/" target="_blank" class="keywords">修改</a>控件的值 //<a href="http://code.js-code.com/tag/sui/" target="_blank" class="keywords">虽</a>然这样能更改控件Text<a href="http://code.js-code.com/tag/shuxing/" target="_blank" class="keywords">属性</a>值，但要进行类型转换，<a href="http://code.js-code.com/tag/zaizheli/" target="_blank" class="keywords">在这里</a>都要转换为字符串类型 private void button1_Click(ob<a href="http://code.js-code.com/tag/je/" target="_blank" class="keywords">je</a>ct sender,RoutedEventArgs <a href="http://code.js-code.com/tag/E/" target="_blank" class="keywords">E)</a> <a href="http://code.js-code.com/tag/" target="_blank" class="keywords">{</a> tbxID.Text = "100"; tbxPrice.Text = "50"; tbx<a href="http://code.js-code.com/tag/titl/" target="_blank" class="keywords">titl</a>e.Text = "SL开发手册"; } } public class Book:INotifyPropertyChanged <a href="http://code.js-code.com/tag/" target="_blank" class="keywords">{</a> privat<a href="http://code.js-code.com/tag/Eint/" target="_blank" class="keywords">E int</a> _id; public <a href="http://code.js-code.com/tag/intid/" target="_blank" class="keywords">int id</a> <a href="http://code.js-code.com/tag/" target="_blank" class="keywords">{</a> get <a href="http://code.js-code.com/tag/" target="_blank" class="keywords">{</a> return _id; } set <a href="http://code.js-code.com/tag/" target="_blank" class="keywords">{</a> _id = value; NotifyPropertyChange("ID"<a href="http://code.js-code.com/tag/" target="_blank" class="keywords">);</a> } } private <a href="http://code.js-code.com/tag/Stri/" target="_blank" class="keywords">Stri</a>ng _<a href="http://code.js-code.com/tag/titl/" target="_blank" class="keywords">titl</a>e; public <a href="http://code.js-code.com/tag/Stri/" target="_blank" class="keywords">Stri</a>ng <a href="http://code.js-code.com/tag/titl/" target="_blank" class="keywords">titl</a>e <a href="http://code.js-code.com/tag/" target="_blank" class="keywords">{</a> get <a href="http://code.js-code.com/tag/" target="_blank" class="keywords">{</a> return _<a href="http://code.js-code.com/tag/titl/" target="_blank" class="keywords">titl</a>e; } set <a href="http://code.js-code.com/tag/" target="_blank" class="keywords">{</a> _<a href="http://code.js-code.com/tag/titl/" target="_blank" class="keywords">titl</a>e = value; NotifyPropertyChange("<a href="http://code.js-code.com/tag/titl/" target="_blank" class="keywords">titl</a>e"<a href="http://code.js-code.com/tag/" target="_blank" class="keywords">);</a> } } private double _price; public double Price <a href="http://code.js-code.com/tag/" target="_blank" class="keywords">{</a> get <a href="http://code.js-code.com/tag/" target="_blank" class="keywords">{</a> return _price; } set <a href="http://code.js-code.com/tag/" target="_blank" class="keywords">{</a> _price = value; NotifyPropertyChange("Price"<a href="http://code.js-code.com/tag/" target="_blank" class="keywords">);</a> } } public event PropertyChangedEventHandler PropertyChanged; private void NotifyPropertyChange(<a href="http://code.js-code.com/tag/Stri/" target="_blank" class="keywords">Stri</a>ng property<a href="http://code.js-code.com/tag/Name/" target="_blank" class="keywords">Name)</a> <a href="http://code.js-code.com/tag/" target="_blank" class="keywords">{</a> if (PropertyChanged <a href="http://code.js-code.com/tag/" target="_blank" class="keywords">!=</a> null) <a href="http://code.js-code.com/tag/" target="_blank" class="keywords">{</a> PropertyChanged(this,new PropertyChangedEventArgs(property<a href="http://code.js-code.com/tag/Name/" target="_blank" class="keywords">Name)</a><a href="http://code.js-code.com/tag/" target="_blank" class="keywords">);</a> } } }

（三）总结：

         数据源--》控件 的更改就只能用OneWay,TwoWay并且需要实现INotifyPropertyChanged接口，而控件---》数据源，只有使用TwoWay方式才可以修改数据源（且不需要实现INotifyPropertyChanged接口）。然而直接更改控件值，虽然这样能更改控件Text属性值，但要进行类型转换，在这里都要转换为字符串类型。所以我们在操作是常用实体来接收参数，而不是直接去控件的值！