如何使用Setter在XAML中设置默认样式？

Question

Via a VisualState Setter, how do I revert a control to its default style?

        <VisualStateGroup>
            <VisualState>
                <VisualState.StateTriggers>
                    <pbixaml:DeviceTypeTrigger DeviceType="Other"/>
                </VisualState.StateTriggers>
                <VisualState.Setters>
                    <Setter Target="flip.Style" Value="{x:Null}"/>
                </VisualState.Setters>
            </VisualState>
        </VisualStateGroup>

I tried using null, but that didn't work (was ignored actually). How do I do that?

Answer 1

You can assign an empty style to the control (kind of hack...):

<VisualStateGroup>
   <VisualState>
      <VisualState.StateTriggers>
         <pbixaml:DeviceTypeTrigger DeviceType="Other"/>
      </VisualState.StateTriggers>
      <VisualState.Setters>
         <Setter Target="flip.Style">
             <Setter.Value>
                 <Style TargetType="FlipView"/>
             </Setter.Value>
         </Setter>
      </VisualState.Setters>
   </VisualState>
</VisualStateGroup>

But I suggest you to do the reverse thing, set the style only in states that you wish, instead of clearing the style in states that you don't.

<VisualStateGroup>
   <VisualState>
      <VisualState.StateTriggers>
         <pbixaml:DeviceTypeTrigger DeviceType="[AllKnown]"/>
      </VisualState.StateTriggers>
      <VisualState.Setters>
         <Setter Target="flip.Style" Value="[What you usually want]"/>      
       </VisualState.Setters>
   </VisualState>
</VisualStateGroup>
..
..
<FlipView .... />   <!-- do not set style here ->

in this way, when the [AllKnown] device type is not active, style is cleared by the visual state manager.

Answer 2

To reset any VisualState setter to a default value, use an empty string.

    <VisualStateGroup>
        <VisualState>
            <VisualState.StateTriggers>
                <pbixaml:DeviceTypeTrigger DeviceType="Other"/>
            </VisualState.StateTriggers>
            <VisualState.Setters>
                <Setter Target="flip.Style" Value=""/>
            </VisualState.Setters>
        </VisualState>
    </VisualStateGroup>

With default value, I mean the style that has been set in your XAML code:

<FlipView x:Name="flip" Text="Test" />

Here your VisualState will revert to the default built-in Windows style.

<FlipView x:Name="flip" Style="{StaticResource MyGreenStyle}" Text="Test" />

Here your VisualState will revert whatever other style used to MyGreenStyle .