Windows Phone应用程序中用户控件的绑定属性

时间:2013-09-28 22:11:40

标签: c# xaml binding windows-phone-8 windows-phone

LongListSelector中,我根据以下DataTemplate显示了多个项目:

<TextBlock Text="{Binding Subject}" TextWrapping="Wrap" Style="{StaticResource PhoneTextExtraLargeStyle}" />
<StackPanel Orientation="Horizontal">
    <TextBlock Text="Last modified :" Margin="15, 0, 5, 0" Foreground="LightGray" Style="{StaticResource PhoneTextNormalStyle}"/>
    <TextBlock Text="{Binding LastModified}" Foreground="#989696" Style="{StaticResource PhoneTextNormalStyle}"/>
 </StackPanel>

此时,一切正常,MVVM和绑定都没问题。

我想将此XAML移动到UserControl并从中绑定这些属性。而且,我曾想过要这样做:

<UserControl x:Class="..."
    xmlns=" ... "
    Foreground="{StaticResource PhoneForegroundBrush}"
    d:DesignHeight="100" d:DesignWidth="480">

    <StackPanel x:Name="LayoutRoot" Background="Transparent">
        <TextBlock x:Name="TitleTextBlock"  Style="{StaticResource PhoneTextExtraLargeStyle}" />
        <StackPanel Orientation="Horizontal">
            <TextBlock Text="Last modified :" Margin="15, 0, 5, 0" Foreground="LightGray" Style="{StaticResource PhoneTextNormalStyle}"/>
            <TextBlock x:Name="LastModifiedDateTextBlock" Foreground="#989696" Style="{StaticResource PhoneTextNormalStyle}"/>
        </StackPanel>
    </StackPanel>
</UserControl>

这是C#类:

public partial class LongListSelectorItemControl
{
    private DateTime _lastModifiedDate;

    public string Title
    {
        get
        {
            return TitleTextBlock.Text;
        }
        set
        {
            TitleTextBlock.Text = value;
        }
    }

    public DateTime LastModifiedDate
    {
        get
        {
            return _lastModifiedDate;
        }
        set
        {
            LastModifiedDateTextBlock.Text = value.ToString(CultureInfo.InvariantCulture);
            _lastModifiedDate = value;
        }
    }

    public LongListSelectorItemControl()
    {
        InitializeComponent();

        _lastModifiedDate = new DateTime();
    }
}

我曾想过以这种方式在XAML中使用用户控件:

<userControls:LongListSelectorItemControl Title="{Binding Subject}" LastModifiedDate="{Binding LastModified}"/>

但出了点问题,我无法弄清楚是什么。我想它必须做一些不正确的绑定...因为在我的应用程序中,一个页面加载了这个XAML我在这个问题中提出,应用程序不会崩溃。然后用户必须导航到另一个页面,其中添加了一些数据并且ViewModel将显示一些数据,所以当它返回到主页面时,这次它只会崩溃...(让我到{{1 Application_UnhandledException中的方法打破调试器。

其他研究

我设法追踪异常,似乎......

MS.Internal.WrappedException: Object of type 'System.Windows.Data.Binding' cannot be converted to type 'System.String'. ---> System.ArgumentException: Object of type 'System.Windows.Data.Binding' cannot be converted to type 'System.String'

我仍然对如何解决这个问题感到困惑......

欢迎任何建议帮助我弄清楚什么是错的。谢谢!

1 个答案:

答案 0 :(得分:5)

为了能够绑定到属性,它必须是dependency property。以下是title属性需要修改的方式:

public partial class LongListSelectorItemControl
{


   public static readonly DependencyProperty TitleProperty =
            DependencyProperty.Register("Title", typeof(string), typeof(LongListSelectorItemControl), new PropertyMetadata(default(string), TitlePropertyChanged));

        private static void TitlePropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            LongListSelectorItemControl myControl=d as LongListSelectorItemControl;
            myControl.TitleTextBlock.Text = e.NewValue as string;
        }

        public string Title
        {
            get { return (string) GetValue(TitleProperty); }
            set { SetValue(TitleProperty, value); }
        }
....
}

您需要使用LastModifiedDate属性执行相同的操作。