Silverlight 4 中数据绑定发生的变化
DependencyObject Binding
在Silverlight之前的版本中,其支持的元素绑定只是允许绑定继承自FrameworkElement类下元素,但是比如一些形变比如Transformations就不能绑定了。现在数据绑定也可以绑定继承自DependencyObject下的任何元素。
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<Grid x:Name="LayoutRoot" Background="White"> <StackPanel Width="400" Margin="0,22,0,0"> <StackPanel.RenderTransform> <CompositeTransform ScaleX="{Binding Value,ElementName=stretcher}" ScaleY="{Binding Value,ElementName=stretcher}" /> </StackPanel.RenderTransform> <Button Content="Button"/> <Button Content="Button"/> <Button Content="Button"/> <Button Content="Button"/> <Button Content="Button"/> </StackPanel> <Slider Minimum=".5" Maximum="4" x:Name="stretcher" Value="1" VerticalAlignment="Top" /> </Grid>
String Formatting
新版的Silverlight4中新增加了格式化字符串的能力。在这之前如果要做一个数据格式化不得不使用一个Converter来格式化字符串。现在可以使用扩展标记StringFormat来做一些比如日期、货币等的格式化。
在VS2010中也提供了可视化的支持。
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<Grid x:Name="LayoutRoot" Background="White"> <TextBox Text="{Binding ReleaseDate, StringFormat='yyyy年MM月dd日', Mode=TwoWay}" Margin="0,30,0,0" Height="26" VerticalAlignment="Top" d:LayoutOverrides="Height" /> <TextBlock Text="{Binding Price, StringFormat='c'}" Margin="0,0,0,0" Height="26" VerticalAlignment="Top" /> </Grid>
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Null and Fallback Values
在某些特殊的情况下,数据有可能加载失败。数据绑定中有新增加了两个宽展标记TargetNullValue、FallbackValue,TargetNullValue这个标记表示了当绑定值是null的时候显示的值。FallbackValue则是在数据未绑定时显示的值。
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<Grid x:Name="LayoutRoot" Background="White"> <TextBlock Text="{Binding Developer, TargetNullValue='(暂无)'}" Height="26" Margin="0,100,0,0" VerticalAlignment="Top" d:LayoutOverrides="Height" /> <TextBlock Text="{Binding Publisher, FallbackValue='(暂无)'}" Height="26" VerticalAlignment="Top" Margin="0,33,0,0" /> </Grid>
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CollectionViewSource Changes
对于在GataGrid中做分组管理,现在的CollectionViewSource支持数据到GroupDescriptions的绑定,这样可以更加轻松的在XAML做分组。
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<UserControl.Resources> <CollectionViewSource x:Name="dataSource" Source="{Binding}"> <CollectionViewSource.GroupDescriptions> <PropertyGroupDescription PropertyName="Gender" /> <PropertyGroupDescription PropertyName="AgeGroup" /> </CollectionViewSource.GroupDescriptions> <CollectionViewSource.SortDescriptions> <compMod:SortDescription PropertyName="AgeGroup" Direction="Ascending"/> </CollectionViewSource.SortDescriptions> </CollectionViewSource> </UserControl.Resources> <Grid x:Name="LayoutRoot" Background="White"> <sdk:DataGrid ItemsSource="{Binding Source={StaticResource dataSource}}" /> </Grid>
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代码
public List<Person> GetPeople()
{
List<Person> peeps = new List<Person>();
peeps.Add(new Person() { FirstName = "Wang", LastName = "Zhe", Gender = "M", AgeGroup = "Adult" });
peeps.Add(new Person() { FirstName = "nasa", LastName = "wang", Gender = "M", AgeGroup = "Adult" });
peeps.Add(new Person() { FirstName = "summer", LastName = "liang", Gender = "F", AgeGroup = "Kid" });
peeps.Add(new Person() { FirstName = "liang", LastName = "jing", Gender = "F", AgeGroup = "Kid" });
return peeps;
}
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Error Propogation
Silverlight的数据验证机制,在这里得到了很多的扩充,提供了IDataErrorInfo、INotifyDataErrorInfo从而能得到更多的信息。