WPF XAML Grid Visibility Trigger

问题:

I have a status message located on the first row of my grid and I want it to slide in and out when the visibility changes.
The first visibility trigger works great and slides the first grid row open quickly. As soon as I add the 'Collapsed' trigger, nothing works at all. How do I reverse the animation to slide closed when the visibility is set to collapsed?

<Grid Grid.Row="0" Height="55" Visibility="{Binding StatusMessageVisibility, Mode=TwoWay}">
    <Grid.Style>
        <Style TargetType="Grid">
            <Style.Triggers>
                <Trigger Property="Visibility" Value="Visible">
                    <Trigger.EnterActions>
                        <BeginStoryboard>
                            <Storyboard>
                                <DoubleAnimation Storyboard.TargetProperty="Height" From="0" To="55" Duration="0:0:.1" />
                            </Storyboard>
                        </BeginStoryboard>
                    </Trigger.EnterActions>
                </Trigger>
                <Trigger Property="Visibility" Value="Collapsed">
                    <Trigger.EnterActions>
                        <BeginStoryboard>
                            <Storyboard>
                                <DoubleAnimation Storyboard.TargetProperty="Height" From="55" To="0" Duration="0:0:.1" />
                            </Storyboard>
                        </BeginStoryboard>
                    </Trigger.EnterActions>
                </Trigger>                        
            </Style.Triggers>
        </Style>
    </Grid.Style>
    <TextBlock Text="Hi There" />
</Grid>

回答1:

You should remove the Visibility binding in your grid and use a DataTrigger that binds to the StatusMessageVisibility property. If you bind the grid's visibility then once it's collapsed it's collapsed and you won't be able to see the animation.

Also, instead of having two data triggers with EnterActions, use a single data trigger that also has an ExitAction for the collapsed state:

<Grid Grid.Row="0" Height="55">
    <Grid.Style>
        <Style TargetType="Grid">
            <Style.Triggers>
                <DataTrigger Binding="{Binding StatusMessageVisibility}" Value="Visible">
                    <DataTrigger.EnterActions>
                        <BeginStoryboard>
                            <Storyboard>
                                <DoubleAnimation Storyboard.TargetProperty="Height" From="0" To="55" Duration="0:0:.1" />
                            </Storyboard>
                        </BeginStoryboard>
                    </DataTrigger.EnterActions>
                    <DataTrigger.ExitActions>
                        <BeginStoryboard>
                            <Storyboard>
                                <DoubleAnimation Storyboard.TargetProperty="Height" From="55" To="0" Duration="0:0:0.1" />
                            </Storyboard>
                        </BeginStoryboard>
                    </DataTrigger.ExitActions>
                </DataTrigger>               
            </Style.Triggers>
        </Style>
    </Grid.Style>
    <TextBlock Text="Hi There" />
</Grid>