运行时动态改变DataContext

本文通过改变DataContext，让ListBox的Item绑定到不同的ObservableCollection。

首先，我们在页面上放一个ListBox，它的ItemsSource绑定设置为strs，
在页面上把一个Button，通过点击这个Button更改DataContext，
xaml代码如下：
[CODE]<phone:PhoneApplicationPage
x:Class="HelloWP7.MainPage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:phone="clr-namespace:Microsoft.Phone.Controls;assembly=Microsoft.Phone"
xmlns:shell="clr-namespace:Microsoft.Phone.Shell;assembly=Microsoft.Phone"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d" d:DesignWidth="480" d:DesignHeight="768"
FontFamily="{StaticResource PhoneFontFamilyNormal}"
FontSize="{StaticResource PhoneFontSizeNormal}"
Foreground="{StaticResource PhoneForegroundBrush}"
SupportedOrientations="Portrait" Orientation="Portrait"
shell:SystemTray.IsVisible="True">

<!--LayoutRoot is the root grid where all page content is placed-->
<Grid x:Name="LayoutRoot" Background="Transparent">
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>

<!--TitlePanel contains the name of the application and page title-->
<StackPanel x:Name="TitlePanel" Grid.Row="0" Margin="12,17,0,28">
<TextBlock x:Name="ApplicationTitle" Text="MY APPLICATION" Style="{StaticResource PhoneTextNormalStyle}"/>
<TextBlock x:Name="PageTitle" Text="page name" Margin="9,-7,0,0" Style="{StaticResource PhoneTextTitle1Style}"/>
</StackPanel>

<!--ContentPanel - place additional content here-->
<Grid x:Name="ContentPanel" Grid.Row="1" Margin="12,0,12,0">
<ListBox Grid.Column="2" Name="listBox1" ItemsSource="{Binding strs}">
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal">
<TextBlock Text="{Binding}" />
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<StackPanel Orientation="Vertical" />
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
</ListBox>
<Button Content="Button" Height="72" HorizontalAlignment="Left" Margin="86,176,0,0" Name="button1" VerticalAlignment="Top" Width="160" Click="button1_Click"/>
</Grid>
</Grid>

<!--Sample code showing usage of ApplicationBar-->
<!--<phone:PhoneApplicationPage.ApplicationBar>
<shell:ApplicationBar IsVisible="True" IsMenuEnabled="True">
<shell:ApplicationBarIconButton IconUri="/Images/appbar_button1.png" Text="Button 1"/>
<shell:ApplicationBarIconButton IconUri="/Images/appbar_button2.png" Text="Button 2"/>
<shell:ApplicationBar.MenuItems>
<shell:ApplicationBarMenuItem Text="MenuItem 1"/>
<shell:ApplicationBarMenuItem Text="MenuItem 2"/>
</shell:ApplicationBar.MenuItems>
</shell:ApplicationBar>
</phone:PhoneApplicationPage.ApplicationBar>-->

</phone:PhoneApplicationPage>[/CODE]
后台代码中，我们声明默认绑定的ObservableCollection：ObservableCollection<string> strs
定义一个test类，这个类中同样定义一个名为strs的ObservableCollection<string>
页面初始化以后设置DataContext为this
[CODE]protected override void OnNavigatedTo(NavigationEventArgs e)
{
DataContext = this;
}[/CODE]
在Button点击以后设置DataContext为test类的实例
[CODE]private void button1_Click(object sender, RoutedEventArgs e)
{
DataContext = _test;
}[/CODE]
全部code behind代码如下：
[CODE]using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Navigation;
using System.Windows.Shapes;
using Microsoft.Phone.Controls;
using System.Collections.ObjectModel;



namespace HelloWP7
{
public partial class MainPage : PhoneApplicationPage
{
private ObservableCollection<string> _strs;
public ObservableCollection<string> strs { get { return _strs; } }

public test _test;

// Constructor
public MainPage()
{
_strs = new ObservableCollection<String> { "hello1", "hello2" };
_test = new test();
InitializeComponent();
}

protected override void OnNavigatedTo(NavigationEventArgs e)
{
DataContext = this;
}

private void button1_Click(object sender, RoutedEventArgs e)
{
DataContext = _test;
}
}

public class test
{
private ObservableCollection<string> _strs;
public ObservableCollection<string> strs { get { return _strs; } }

public test()
{
_strs = new ObservableCollection<String> { "world1", "world2" };
}
};
}[/CODE]

Regards
Vincent
[url]http://weibo.com/xueyw[/url]