与 Prism/RibbonControl 的多重绑定导致转换器过早触发

Question

    <inf:WorkspaceContent.Resources>
    <ResourceDictionary>
        <commands:CommandReference x:Key="CompareCommandReference" Command="{Binding CompareCommand}"/>
        <converters:FlowDocumentConverter x:Key="FlowDocConverter"/>
    </ResourceDictionary>
</inf:WorkspaceContent.Resources>

<Grid x:Name="LayoutRoot">
    <Grid.RowDefinitions>
        <RowDefinition/>
        <RowDefinition Height="Auto"/>
        <RowDefinition Height="Auto"/>
    </Grid.RowDefinitions>
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="0.5*"/>
        <ColumnDefinition Width="0.5*"/>
    </Grid.ColumnDefinitions>
    <RichTextBox x:Name="OrigText" Margin="0,0,8,0" d:LayoutOverrides="Width">
        <FlowDocument>
            <Paragraph><Run Text="The fox jumped over the hill. The fox jumped over the mountain."/></Paragraph>
            <Paragraph><Run Text=""/></Paragraph>
        </FlowDocument>
    </RichTextBox>
    <Button x:Name="OrigFileBrowse" HorizontalAlignment="Center" Margin="0,0,8,2.442" Width="75" Content="Browse" Grid.Row="1" d:LayoutOverrides="Height"/>
    <RichTextBox x:Name="ModifiedText" Grid.Column="1" Margin="8,0,0,0">
        <FlowDocument>
            <Paragraph><Run Text="The fox junped over the hill. The fax jumped over the mountain."/></Paragraph>
        </FlowDocument>
    </RichTextBox>
    <Button x:Name="ModifiedFileBrowse" HorizontalAlignment="Center" Width="75" Content="Browse" Grid.Row="1" Grid.Column="1" Margin="0,0,0,2.442" d:LayoutOverrides="Height"/>
    <Button x:Name="Compare" Command="{StaticResource CompareCommandReference}" HorizontalAlignment="Center" VerticalAlignment="Top" Width="75" Content="Compare" Grid.Row="2" Grid.ColumnSpan="2">
        <Button.CommandParameter>
            <MultiBinding Converter="{StaticResource FlowDocConverter}">
                <Binding Path="Document" ElementName="OrigText"/>
                <Binding Path="Document" ElementName="ModifiedText"/>
            </MultiBinding>
        </Button.CommandParameter>
    </Button>
</Grid>

上面是问题的 XAML...我有一个按钮，单击该按钮时会通过 Prism 中的 IEventAggregator 发布一个事件，并传入上面的视图。然后转换器启动，并且这些值看起来是合法的。不过，我希望在上面触发比较命令时触发比较。但是当这种情况发生时，object[] 有 2 个项目都是 null...不知道是什么原因导致的？

Answer 1

这是设计使然。由于底层 FlowDocument 引用不会更改，因此它将被缓存。解决方案不是将项目作为简单的 object[] 返回，而是作为新定义的类型返回。一旦执行此操作，执行比较命令时，值将通过参数返回。