WPF Mouse Over Style Trigger

<Grid>
  <Grid.ColumnDefinitions>
    <ColumnDefinition Width="25" />
    <ColumnDefinition />
  </Grid.ColumnDefinitions>
  
  <Button Grid.Column="1">A Button</Button>

  <Grid.Style>
    <Style TargetType="{x:Type Grid}">
      <Style.Triggers>
        <Trigger Property="IsMouseOver" Value="False">
          <Setter Property="Opacity" Value="0.5"></Setter>
        </Trigger>
        <Trigger Property="IsMouseOver" Value="True">
          <Setter Property="Opacity" Value="1"></Setter>
        </Trigger>
      </Style.Triggers>
    </Style>
  </Grid.Style>
</Grid>
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