AG_E_PARSER_BAD_PROPERTY_VALUE [Line: 7 Position: 121] error

我得到这个错误，但我看不到我的xaml有什么问题。我检查了三遍。什么好主意吗?

    <controls:PanoramaItem Header="first item">
        <!--Double line list with text wrapping-->
        <ListBox Margin="0,0,-12,0" ItemsSource="{Binding Items}">
            <ListBox.ItemTemplate>
                <DataTemplate>
                    <Grid Margin="0,0,0,17" Width="450">
                        <Grid.ColumnDefinitions>
                            <ColumnDefinition Width="200" />
                            <ColumnDefinition Width="50"/>
                            <ColumnDefinition Width="200" />
                        </Grid.ColumnDefinitions>
                        <Image Source="{Binding Url}" Stretch="None" HorizontalAlignment="Left" Grid.Column="1" MouseEnter="Image_MouseEnter"></Image>
                        <TextBlock Text="{Binding Title}" HorizontalAlignment="Right" TextWrapping="Wrap" Grid.Column="2" />
                    </Grid>
                </DataTemplate>
            </ListBox.ItemTemplate>
        </ListBox>
    </controls:PanoramaItem>