How to target all controls (WPF Styles)

Can I specify a style that applies to all elements? I tried

<Style TargetType="Control">
    <Setter Property="Margin" Value="0,5" />
</Style>

But it did nothing

The Style you created is only targeting Control and not elements that derive from Control. When you don't set the x:Key it's implicitly set to the TargetType, so in your case x:Key="{x:Type Control}".

There isn't any direct way to specify a Style that targets all elements that derive from the TargetType of the Style. You have some other options.

If you have the following Style

<Style x:Key="ControlBaseStyle" TargetType="{x:Type Control}">
    <Setter Property="Margin" Value="50" />
</Style>

You can target all Buttons for example

<Style TargetType="{x:Type Button}" BasedOn="{StaticResource ControlBaseStyle}"/>

or use the style directly on any element, e.g. Button

<Button Style="{StaticResource ControlBaseStyle}" ...>

As Fredrik Hedblad answered you can effect all elements that inherited from control.

But you can't apply style for textblock and button with the same style for example.

to do that:

    <Style x:Key="DefaultStyle" TargetType="{x:Type FrameworkElement}">
        <Setter Property="Control.Margin" Value="50"/>
    </Style>
    <Style TargetType="TextBlock" BasedOn="{StaticResource DefaultStyle}"/>
    <Style TargetType="Button" BasedOn="{StaticResource DefaultStyle}"/>