具有可綁定集合的Xaml WinRT自定義用戶控件

Question

我正在嘗試制作一個自定義用戶控件，以便可以在所有視圖中重復使用。 我的BaseViewModel具有一個稱為ViewAlerts的屬性，該屬性用於在整個應用程序中始終顯示警報（例如成功更新，失敗請求等）。 我能夠達到自定義控件是可構建的並且具有綁定屬性的地步，但是警報的集合從未顯示。 我出於測試目的在基視圖模型中靜態定義了一些警報，但無法使警報顯示（似乎是INotifyPropertyChanged的問題，但是我的bindable屬性繼承自ObservableCollection <>，因此它應該自動處理認為）。

到目前為止，這是我的自定義控件：

    <UserControl.Resources>
        <ResourceDictionary>
            <ResourceDictionary.MergedDictionaries>
                <ResourceDictionary Source="../../Resources/MMJCeoResources.xaml" />
                <ResourceDictionary>
                    <Style TargetType="TextBlock" x:Key="AlertTextStyle">
                        <Setter Property="FontSize" Value="15"></Setter>
                        <Setter Property="Margin" Value="10" />
                        <Setter Property="Padding" Value="10" />
                    </Style>
                    <DataTemplate x:Key="DangerAlert">
                        <Grid Background="LightPink">
                            <Grid.RowDefinitions>
                                <RowDefinition Height="*" />
                                <RowDefinition Height="10*"/>
                            </Grid.RowDefinitions>
                            <Border Width="10"
                                    Height="10"
                                    BorderBrush="DarkRed"
                                    HorizontalAlignment="Right"
                                    Margin="5"
                                    Grid.Row="0">
                                    <TextBlock Text="X" />
                            </Border>
                            <TextBlock Grid.Row="1" Text="{Binding Message}" Style="{StaticResource AlertTextStyle}" Foreground="DarkRed"/>
                        </Grid>
                    </DataTemplate>
                    <DataTemplate x:Key="SuccessAlert">
                        <Grid Background="LightGreen">
                            <Grid.RowDefinitions>
                                <RowDefinition Height="*" />
                                <RowDefinition Height="10*"/>
                            </Grid.RowDefinitions>
                            <Border Width="10"
                                    Height="10"
                                    BorderBrush="DarkGreen"
                                    HorizontalAlignment="Right"
                                    Margin="5"
                                    Grid.Row="0">
                                <TextBlock Text="X" />
                            </Border>
                            <TextBlock Grid.Row="1" Text="{Binding Message}" Style="{StaticResource AlertTextStyle}" Foreground="DarkGreen"/>
                        </Grid>
                    </DataTemplate>
                    <DataTemplate x:Key="InfoAlert">
                        <Grid Background="LightGreen">
                            <Grid.RowDefinitions>
                                <RowDefinition Height="*" />
                                <RowDefinition Height="10*"/>
                            </Grid.RowDefinitions>
                            <Border Width="10"
                                    Height="10"
                                    BorderBrush="DarkGreen"
                                    HorizontalAlignment="Right"
                                    Margin="5"
                                    Grid.Row="0">
                                <TextBlock Text="X" />
                            </Border>
                            <TextBlock Grid.Row="1" Text="{Binding Message}" Style="{StaticResource AlertTextStyle}" Foreground="DarkGreen"/>
                        </Grid>
                    </DataTemplate>
                    <DataTemplate x:Key="WarningAlert">
                        <Grid Background="LightSalmon">
                            <Grid.RowDefinitions>
                                <RowDefinition Height="*" />
                                <RowDefinition Height="10*"/>
                            </Grid.RowDefinitions>
                            <Border Width="10"
                                    Height="10"
                                    BorderBrush="DarkOrange"
                                    HorizontalAlignment="Right"
                                    Margin="5"
                                    Grid.Row="0">
                                <TextBlock Text="X" />
                            </Border>
                            <TextBlock Grid.Row="1" Text="{Binding Message}" Style="{StaticResource AlertTextStyle}" Foreground="DarkOrange"/>
                        </Grid>
                    </DataTemplate>
                </ResourceDictionary>
            </ResourceDictionary.MergedDictionaries>
        </ResourceDictionary>
    </UserControl.Resources>

    <Grid>
        <ItemsControl ItemsSource="{Binding Path=Alerts}"
                      ItemTemplateSelector="{StaticResource AlertDataTemplateSelector}">

        </ItemsControl>
    </Grid>
</UserControl>

該控件的背后代碼：

public sealed partial class AlertControl : UserControl
{
    public static readonly DependencyProperty AlertsProperty = DependencyProperty.Register(
        "Alerts", typeof (ObservableList<Alert>), typeof (AlertControl), new PropertyMetadata(default(ObservableList<Alert>), OnAlertsChanged));

    public ObservableList<Alert> Alerts
    {
        get { return (ObservableList<Alert>) GetValue(AlertsProperty); }
        set { SetValue(AlertsProperty, value); }
    }
    //I was trying to adapt another tutorial to what I was trying to accomplish but only got this far
    public static void OnAlertsChanged(object sender, DependencyPropertyChangedEventArgs e)
    {
        var old = e.OldValue as ObservableList<Alert>;
        var me = sender as AlertControl;

        if (old != null)
        {
            old.CollectionChanged -= me.OnAlertCollectionChanged;
        }

        var n = e.NewValue as ObservableList<Alert>;
        if (n != null)
            n.CollectionChanged += me.OnAlertCollectionChanged;
    }

    private void OnAlertCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
    {
        if (e.Action == NotifyCollectionChangedAction.Reset)
        {
            Alerts.Clear();
            var n = e.NewItems as ObservableList<Alert>;
            Alerts.AddRange(n);
        }


    }
    public AlertControl()
    {
        this.InitializeComponent();
        DataContext = this;

    }
}

一個示例實現：

 <Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">

    <StackPanel Orientation="Vertical" HorizontalAlignment="Stretch">
        <TextBlock Style="{StaticResource PageTitle}" Text="User Information" />
        <controls:AlertControl Alerts="{Binding ViewAlerts}" />

在此實現中，ViewAlerts屬性中具有4個靜態定義的警報，因此我知道應該顯示一些值。

Answer 1

您應該為此內部Grid而不是控件本身提供DataContext，因為外部綁定將在控件內部搜索ViewAlerts

<Grid x:Name="InnerGrid">
    <ItemsControl ItemsSource="{Binding Path=Alerts}"
                  ItemTemplateSelector="{StaticResource AlertDataTemplateSelector}">

    </ItemsControl>
</Grid>


public AlertControl()
{
    this.InitializeComponent();
    InnerGrid.DataContext = this;
}

之后，您可以綁定到警報，警報將被綁定到InnerGrid內部的ItemsControl。