WPF DataTrigger数据触发器

1.通过绑定的属性值变化，动态改变界面的显示，比如绑定了IsExpanded，当为true，grid高度变成600，反之，grid高度变成320.

        <Grid.Style>
                             <Style TargetType="Grid">
                                 <Style.Triggers>
                                     <DataTrigger Binding="{Binding IsExpanded}" Value="true">
                                         <DataTrigger.EnterActions>
                                             <BeginStoryboard>
                                                 <Storyboard  >
                                                     <DoubleAnimation From="320"
                                                                      To="600"
                                                                      Duration="0:0:1"
                                                                      Storyboard.TargetProperty="Height"></DoubleAnimation>
                                                 </Storyboard>
                                             </BeginStoryboard>
                                         </DataTrigger.EnterActions>
                                         <DataTrigger.ExitActions>
                                             <BeginStoryboard>
                                                 <Storyboard>
                                                     <DoubleAnimation From="600"
                                                                      To="320"
                                                                      Duration="0:0:1"
                                                                      Storyboard.TargetProperty="Height"></DoubleAnimation>
                                                 </Storyboard>
                                             </BeginStoryboard>
                                         </DataTrigger.ExitActions>

                                     </DataTrigger>
                                 </Style.Triggers>
                             </Style>
                         </Grid.Style>