GENERAL: XAML Markup TextBlock.Style as attribute

I have style defined im my Page resources like this:
<Style x:Key="Txt_1" TargetType="TextBlock">
   <Setter Property="Padding" Value="0,5,0,5"/>
</Style>

then I use it for elements in stack panel and it works well:
<StackPanel>
    <TextBlock Style="{StaticResource Txt_1}">sample 1</TextBlock>
    <TextBlock Style="{StaticResource Txt_1}">sample 2</TextBlock>
</StackPanel>

As long as I want all TextBlock inside StackPanel to be the same style I tried this:
<StackPanel TextBlock.Style="{StaticResource Txt_1}">
    <TextBlock>sample 1</TextBlock>
    <TextBlock>sample 2</TextBlock>
</StackPanel>

This approach works well with for example "FontWeight" property but not with "Style". I use your MarkupPad to test it.

Thanks for explanation.

As far as this style is global for page I don't want to define it many times in different panels. I made such workaround :)

<StackPanel>
<StackPanel.Resources>
   <Style TargetType="TextBlock" BasedOn="{StaticResource Txt_1}"/>
</StackPanel.Resources>
   <TextBlock>sample 1</TextBlock>
   <TextBlock>sample 2</TextBlock>
</StackPanel>