Seliverlight 中数据绑定INotifyPropertyChanged 接口的用法 .数据绑定IValueConvert的用法学习笔记

1.数据绑定
/// 数据绑定是数据源和目标数据之间的一座桥梁 在Silverlighth中这座桥梁有三个方向
/// oneWay
/// TwoWay
/// OneTime
/// INotifyPropertyChanged
///using System.ComponentModel;
/// 是告诉我们通知的对象
/// 我们还需要以为信使来完成这个通知
/// 更改通知就是数据绑定这座桥梁的信使
/// 它根据数据流方向来通知数据源和目标数据对方的变化
/// 要实现接口我们需要实现INotifyPropertyChanged接口，INotifyPropertyChanged具有PropertyChanged 事件
/// 该事件通知绑定引擎源以更改，以便可以更新目标值，
2.数据绑定 在Seliverlight中实现数据转换 需要创建数据转换类 并实先IValueConvert接口的Convert方法和ConvertBack方法
当数据源传递给目标时调用Convert方法 反之调用ConvertBack方法 Converback方法不可省落。

[ValueConversion(typeof(DateTime), typeof(String))]
public class DateConverter : IValueConverter
{
//在将原数据传递到目标以在Ui显示之前 对原数据进行修改
//object value,正转递到目标的元数据，
// Type targetType,目标依赖项属性需要的数据的System.Type
// object parameter, 要在转换器逻辑中使用的可选参数
// CultureInfo culture 转换的区域性
//返回结构 要传递到目标依赖项属性的值
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
DateTime date = (DateTime)value;
return date.ToShortDateString();
}

//再将目标数据传递到原对象之前，对目标数据进行修改
//System.Window.Data.BindingMode.TwoWay 绑定中进行调用
//object value,正转递到元的目标数据，
// Type targetType,源对象需要的数据的System.Type
// object parameter, 要在转换器逻辑中使用的可选参数
// CultureInfo culture 转换的区域性
//返回结构 要传递到源对象的值
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
string strValue = value as string;
DateTime resultDateTime;
if (DateTime.TryParse(strValue, out resultDateTime))
{
return resultDateTime;
}
return DependencyProperty.UnsetValue;
}
}
///数据转换的使用，在Xaml页面中加入转换代码myConverter,在使用前 在UserControl元素中声明命名空间
///xmlns:my="clr-namespace:Sample"
<UserControl x:Class="ConverterParameterEx.Page"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:ConverterParameterEx"
Width="400" Height="300">
<Grid x:Name="LayoutRoot" Background="White">
<Grid.Resources>
<local:DateFormatter x:Key="FormatConverter" />
</Grid.Resources>

<ComboBox Height="60" Width="200" x:Name="MusicCombo"
ItemsSource="{Binding}">
<ComboBox.ItemTemplate>
<DataTemplate>
<StackPanel>
<TextBlock FontWeight="Bold" Text="{Binding Path=Name, Mode=OneWay}" />
<TextBlock Text="{Binding Path=Artist, Mode=OneWay}" />
<TextBlock Text="{Binding Path=ReleaseDate, Mode=OneWay,
Converter={StaticResource FormatConverter},
ConverterParameter=\{0:d\}}" />
</StackPanel>
</DataTemplate>
</ComboBox.ItemTemplate>
</ComboBox>
</Grid>
</UserControl>

using System;
using System.Collections.ObjectModel;
using System.Windows.Controls;
using System.Windows.Data;

namespace ConverterParameterEx
{
public partial class Page : UserControl
{

public ObservableCollection<Recording> MyMusic =
new ObservableCollection<Recording>();
public Page()
{
InitializeComponent();

// Add items to the collection.
MyMusic.Add(new Recording("Chris Sells", "Chris Sells Live",
new DateTime(2008, 2, 5)));
MyMusic.Add(new Recording("Luka Abrus",
"The Road to Redmond", new DateTime(2007, 4, 3)));
MyMusic.Add(new Recording("Jim Hance",
"The Best of Jim Hance", new DateTime(2007, 2, 6)));

// Set the data context for the combo box.
MusicCombo.DataContext = MyMusic;
}
}

// Simple business object.
public class Recording
{
public Recording() { }
public Recording(string artistName, string cdName, DateTime release)
{
Artist = artistName;
Name = cdName;
ReleaseDate = release;
}
public string Artist { get; set; }
public string Name { get; set; }
public DateTime ReleaseDate { get; set; }
}

public class DateFormatter : IValueConverter
{
// This converts the DateTime object to the string to display.
public object Convert(object value, Type targetType, object parameter,
System.Globalization.CultureInfo culture)
{
// Retrieve the format string and use it to format the value.
string formatString = parameter as string;
if (!string.IsNullOrEmpty(formatString))
{
return string.Format(culture, formatString, value);

}
// If the format string is null or empty, simply call ToString()
// on the value.
return value.ToString();
}

// No need to implement converting back on a one-way binding
public object ConvertBack(object value, Type targetType,
object parameter, System.Globalization.CultureInfo culture)
{
throw new NotImplementedException();
}
}
}