WPF使用小结:(1)XmlDataProvider数据源，为什么不显示内容

在WPF中，我们可能有些一些数据是静态的，但是是一个迭代的列表显示的内容。MSDN建议使用XmlDataProvider。代码如下

  <StackPanel x:Name="pn_TaskStatusPanel" Background="#cee8ff" Orientation="Vertical">
        <StackPanel.Resources>
            <XmlDataProvider x:Key="dataTaskStatus" XPath="/Tasks">
                <x:XData>
                    <Tasks xmlns="">
                        <Task>
                            <ImagePath>D:\model1.png</ImagePath>
                            <Name>XXX</Name>
                            <Count>20</Count>
                        </Task>
                        <Task>
                            <ImagePath>D:\model1.png</ImagePath>
                            <Name>XxXX</Name>
                            <Count>20</Count>
                        </Task>
                        <Task>
                            <ImagePath>D:\model1.png</ImagePath>
                            <Name>XXX</Name>
                            <Count>20</Count>
                        </Task>
                        <Task>
                            <ImagePath>D:\model1.png</ImagePath>
                            <Name>XXXX</Name>
                            <Count>20</Count>
                        </Task>
                    </Tasks>
                </x:XData>
            </XmlDataProvider>
        </StackPanel.Resources>
        <ListView x:Name="lv_Status" Height="200" Background="#cee8ff" ItemsSource="{Binding Source={StaticResource dataTaskStatus},XPath=Task}" >
            <ListView.ItemContainerStyle>
                <Style TargetType="{x:Type ListViewItem}">
                    <Setter Property="Background" Value="#cee8ff"/>                    
                    <Style.Triggers>
                        <Trigger Property="IsMouseOver" Value="True">
                            <Setter Property="Background" Value="#d6edff" />
                            
                        </Trigger>
                    </Style.Triggers>                    
                </Style>
            </ListView.ItemContainerStyle>
            <ListView.ItemTemplate>
                <DataTemplate>
                    <Border  Height="50" Width="100" Margin="5" BorderThickness="1" BorderBrush="SteelBlue" CornerRadius="3" HorizontalAlignment="Stretch" >
                        <Grid Margin="3" ShowGridLines="True" HorizontalAlignment="Stretch" >
                            <Grid.RowDefinitions>
                                <RowDefinition Height="25"></RowDefinition>
                                <RowDefinition Height="25"></RowDefinition>                                
                            </Grid.RowDefinitions>
                            <Grid.ColumnDefinitions>
                                <ColumnDefinition></ColumnDefinition>
                                <ColumnDefinition ></ColumnDefinition>
                            </Grid.ColumnDefinitions>
                            <Image Source="{Binding XPath=ImagePath}" Grid.Column="0" Grid.Row="0" Grid.RowSpan="2" />
                            <Label Content="{Binding XPath=Name}" Grid.Column="1" Grid.Row="0" Grid.IsSharedSizeScope="True" ></Label>
                            <Label Content="{Binding XPath=Count}" Grid.Column="1" Grid.Row="1"></Label>
                        </Grid>
                    </Border>
                </DataTemplate>
            </ListView.ItemTemplate>
        </ListView>

注意。这里面有一个MSDN提示，XmlDataProvider中注意的地方。

必须声明： xmlns=""   否则 XPath搜寻路径会失灵。

MSDN原文解释。

The root node of the XML data has an xmlns attribute that sets the XML namespace to an empty string. This is a requirement for applying XPath queries to a data island that is inline within the XAML page. In this inline case, the XAML, and thus the data island, inherits the System.Windows namespace. Because of this, you need to set the namespace blank to keep XPath queries from being qualified by the System.Windows namespace, which would misdirect the queries.