c# - 使用交互 wpf 时出现 Xaml 错误

Question

使用时出现以下错误Interactivity：

错误集合属性“System.Windows.Controls.Canvas”。“触发器”为空。

这是我的代码：

<ItemsControl x:Name="StreamCanvasItemSource" ItemsSource="{Binding StreamCanvasItems, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" Width="{Binding ActualWidth, ElementName=StreamImage}" Height="{Binding ActualHeight, ElementName=StreamImage}">
    <ItemsControl.ItemsPanel>
        <ItemsPanelTemplate>
            <Canvas x:Name="StreamCanvas" Background="Transparent" Width="{Binding ActualWidth, ElementName=StreamImage}" Height="{Binding ActualHeight, ElementName=StreamImage}" 
                AuxiliaryUtils:SizeObserver.Observe="True" AuxiliaryUtils:SizeObserver.ObservedWidth="{Binding CurrentCanvasWidth, Mode=OneWayToSource}" 
                AuxiliaryUtils:SizeObserver.ObservedHeight="{Binding CurrentCanvasHeight, Mode=OneWayToSource}" 
                AuxiliaryUtils:SizeObserver.ObservedLeft="{Binding CanvasLeft, Mode=OneWayToSource}" AuxiliaryUtils:SizeObserver.ObservedTop="{Binding CanvasTop, Mode=OneWayToSource}">
                <Interactivity:Interaction.Triggers>
                    <Interactivity:EventTrigger EventName="PreviewMouseWheel">
                        <Command:EventToCommand Command="{Binding OnMouseWheelCommand}" PassEventArgsToCommand="True" />
                    </Interactivity:EventTrigger>
                    <Interactivity:EventTrigger EventName="PreviewMouseDown">
                        <Interactivity:InvokeCommandAction Command="{Binding OnMouseDownCommand}" CommandParameter="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Canvas}}}"/>
                    </Interactivity:EventTrigger>
                    <Interactivity:EventTrigger EventName="PreviewMouseMove">
                        <Interactivity:InvokeCommandAction Command="{Binding OnMouseMoveCommand}" CommandParameter="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Canvas}}}"/>
                    </Interactivity:EventTrigger>
                    <Interactivity:EventTrigger EventName="PreviewMouseUp">
                        <Interactivity:InvokeCommandAction Command="{Binding OnMouseUpCommand}" CommandParameter="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Canvas}}}"/>
                    </Interactivity:EventTrigger>
                </Interactivity:Interaction.Triggers>
            </Canvas>
        </ItemsPanelTemplate>
  </ItemsControl.ItemsPanel>
</ItemsControl>

Interactivity问题是当我运行程序时一切都按预期工作，我在编译时看到错误，除非我评论该块，否则我看不到设计器。

知道为什么吗？

Answer 1

数据上下文如何连接到窗口/页面？建议将以下行添加到窗口/页面并将 IsDesignTimeCreatable 设置为 true：

d:DataContext="{d:DesignInstance Type=yourviewmodetype, IsDesignTimeCreatable=True}"

通过这种方式，视图将在设计时绑定到视图模型的值，这正是您的应用程序中出现问题的地方。