How to target a group of controls in a storyboard WPF - wpf

Question

<Storyboard x:Key="OnClick1">
<DoubleAnimation Storyboard.TargetName="{StaticResource test}"
Storyboard.TargetProperty="Opacity"
From="1"
To="0"
RepeatBehavior="2000"
AutoReverse="True"
Duration="0:0:0.7"/>
</Storyboard>
<Window.Triggers>
<EventTrigger RoutedEvent="ButtonBase.Loaded" SourceName="button">
<BeginStoryboard Storyboard="{StaticResource OnClick1}"/>
</EventTrigger>
</Window.Triggers>
<Button x:Name="button2" x:key="test" Content="Button" Margin="234,140,164,0" Height="37" VerticalAlignment="Top"/>
<Button x:Name="button3" x:key="test" Content="Button" Margin="234,140,164,0" Height="37" VerticalAlignment="Top"/>
I am trying to add this double animation to multiple buttons without duplicating the double animation. Initially, I had the TargetName set to the name of the first button and it works but if added key to the button I get this message "The property "key" does not exist in WinFX namespace.

Answer 1

Give ButtonA the storyboard that drives its Opacity. For each other button,
<Button
x:Name="button3"
Opacity="{Binding Opacity, ElementName=button2}"
...
/>
Alternatively, put all the buttons inside a StackPanel (or Grid, or whatever), and animate the parent's Opacity.

Answer 2

The sample markup you have posted doesn't provide a reproducible sample of your issue but you could add a trigger to each Button that you want to animate:
<Window x:Class="WpfApplication1.Window1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d"
Title="Window1" Height="300" Width="300">
<Window.Resources>
<Storyboard x:Key="OnClick1">
<DoubleAnimation
Storyboard.TargetProperty="Opacity"
From="1"
To="0"
RepeatBehavior="2000"
AutoReverse="True"
Duration="0:0:0.7"/>
</Storyboard>
</Window.Resources>
<StackPanel>
<Button x:Name="button2" Content="Button" Height="37" VerticalAlignment="Top">
<Button.Triggers>
<EventTrigger RoutedEvent="Loaded">
<BeginStoryboard Storyboard="{StaticResource OnClick1}"/>
</EventTrigger>
</Button.Triggers>
</Button>
<Button x:Name="button3" Content="Button" Height="37" VerticalAlignment="Top">
<Button.Triggers>
<EventTrigger RoutedEvent="Loaded">
<BeginStoryboard Storyboard="{StaticResource OnClick1}"/>
</EventTrigger>
</Button.Triggers>
</Button>
</StackPanel>
</Window>