基于 DependencyProperty 的 UserControl 中的触发触发器

Question

有一个非常简单的问题，但我似乎无法在 Internet 上找到答案。可能是因为我没有找对地方。

我有一个具有自定义枚举类型的 DependencyProperty 的用户控件。 在 XAML 中，我想根据枚举类型的值显示/隐藏元素。我尝试使用 DataTriggers 执行此操作，但无法正常工作。

<UserControl x:Class="WpfApplication1.DisplayIcon"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
         xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
         mc:Ignorable="d" 
         d:DesignHeight="50" d:DesignWidth="50"
         x:Name="control">
<UserControl.Resources>
    <Style TargetType="Ellipse">
        <Setter Property="Visibility" Value="Collapsed"/>
        <Style.Triggers>
            <DataTrigger Value="Ellipse" Binding="{Binding MyIconType, ElementName=control}">
                <Setter Property="Visibility" Value="Visible"/>
            </DataTrigger>
        </Style.Triggers>
    </Style>

    <Style TargetType="Rectangle">
        <Setter Property="Visibility" Value="Collapsed"/>
        <Style.Triggers>
            <DataTrigger Value="Rectangle" Binding="{Binding MyIconType, ElementName=control}">
                <Setter Property="Visibility" Value="Visible"/>
            </DataTrigger>
        </Style.Triggers>
    </Style>

</UserControl.Resources>
<Grid>
    <Ellipse x:Name="el1" Fill="Red" Width="30" Height="30" />
    <Rectangle x:Name="el2" Fill="Green" Width="20" Height="20" /> 
    <TextBlock Text="{Binding MyIconType, ElementName=control}" Margin="0,40,0,0"/>
</Grid></UserControl>

我的代码如下所示：

public enum IconType
{
    Ellipse,
    Rectangle
}
public partial class DisplayIcon : UserControl
{
    public DisplayIcon()
    {
        InitializeComponent();
    }

    public IconType MyIconType
    {
        get { return (IconType)GetValue(MyIconTypeProperty); }
        set { SetValue(MyIconTypeProperty, value); }
    }

    // Using a DependencyProperty as the backing store for MyIconType.  This enables animation, styling, binding, etc...
    public static readonly DependencyProperty MyIconTypeProperty =
        DependencyProperty.Register("MyIconType", typeof(IconType), typeof(DisplayIcon), new PropertyMetadata(IconType.Ellipse));

}

有人可以帮我吗？

谢谢，

吉姆

Answer 1

您可以为每个元素创建一个Style 并在那里定义触发器：

<UserControl x:Class="WpfApplication1.DisplayIcon"
     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
     xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
     xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
     mc:Ignorable="d" 
     d:DesignHeight="50" d:DesignWidth="50"
     x:Name="control">

<UserControl.Resources>

    <Style TargetType="Ellipse">
        <Style.Triggers>
            <DataTrigger Value="Rectangle" Binding="{Binding MyIconType, ElementName=control}">
                <Setter Property="Visibility" Value="Collapsed"/>
            </DataTrigger>
        </Style.Triggers>
    </Style>

    <Style TargetType="Rectangle">
        <Style.Triggers>
            <DataTrigger Value="Ellipse" Binding="{Binding MyIconType, ElementName=control}">
                <Setter Property="Visibility" Value="Collapsed"/>
            </DataTrigger>
        </Style.Triggers>
    </Style>

</UserControl.Resources>

<Grid>
    <Ellipse x:Name="el1" Fill="Red" Width="20" Height="20"/>
    <Rectangle Grid.Row="1" x:Name="el2" Fill="Green" Width="20" Height="20"/>
</Grid>

编辑：

事实上，反转Visibility 逻辑可能更有意义。这样您就可以添加形状而无需修改代码：

<UserControl x:Class="WpfApplication1.DisplayIcon"
     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
     xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
     xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
     mc:Ignorable="d" 
     d:DesignHeight="50" d:DesignWidth="50"
     x:Name="control">

<UserControl.Resources>

    <Style TargetType="Ellipse">
        <Setter Property="Visibility" Value="Collapsed"/>
        <Style.Triggers>
            <DataTrigger Value="Ellipse" Binding="{Binding MyIconType, ElementName=control}">
                <Setter Property="Visibility" Value="Visible"/>
            </DataTrigger>
        </Style.Triggers>
    </Style>

    <Style TargetType="Rectangle">
        <Setter Property="Visibility" Value="Collapsed"/>
        <Style.Triggers>
            <DataTrigger Value="Rectangle" Binding="{Binding MyIconType, ElementName=control}">
                <Setter Property="Visibility" Value="Visible"/>
            </DataTrigger>
        </Style.Triggers>
    </Style>

</UserControl.Resources>

<Grid>
    <Ellipse x:Name="el1" Fill="Red" Width="20" Height="20"/>
    <Rectangle x:Name="el2" Fill="Green" Width="20" Height="20"/>
</Grid>