How to create a storyboard and rotate an image in wpf using c # code

I'm starting with WPF (when I was used to use winforms).

I am trying to rotate the image and want to use the storyboard, as in the following phases, I need to add some animations running in time.

my code is inside the button click event:

//start the animation
            DoubleAnimation animationRotation = new DoubleAnimation();

            animationRotation.From = -17;
            animationRotation.To = 17;
            animationRotation.Duration = new Duration(TimeSpan.FromMilliseconds(NumericDisplay.Milliseconds));
            animationRotation.RepeatBehavior = RepeatBehavior.Forever;
            animationRotation.AccelerationRatio = 0.3;
            animationRotation.DecelerationRatio = 0.3;
            animationRotation.AutoReverse = true;

            Storyboard storyboard = new Storyboard();

            Storyboard.SetTarget(animationRotation, Arm);
            Storyboard.SetTargetProperty(animationRotation,
              new PropertyPath("(UIElement.RenderTransform).(TransformGroup.Children)[0].(RotateTransform.Angle)")); 

            storyboard.Children.Add(animationRotation);

            // Add the storyboard to the tracking collection.      
            //this.Stostoryboards.Add(bomb, storyboard);

            // Configure and start the storyboard.
            this.BeginStoryboard(storyboard);

the code compiles without warning, but the click event does not start the animation,

EDIT One of the suggested answers asked me to verify that XAML contains a definition for rotatetransform ... the XAML below is what I use

<UserControl
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"
xmlns:my="clr-namespace:MetronomeLibrary" xmlns:Microsoft_Windows_Themes="clr-namespace:Microsoft.Windows.Themes;assembly=PresentationFramework.Aero"
mc:Ignorable="d"
x:Class="MetronomeLibrary.MetronomeLarge"
x:Name="UserControl" Height="386" Width="1024" SizeChanged="UserControl_SizeChanged">
<UserControl.Resources>
    <ResourceDictionary>
        <ResourceDictionary.MergedDictionaries>
            <ResourceDictionary Source="ResourceDictionary.xaml"/>
        </ResourceDictionary.MergedDictionaries>
        <ImageBrush x:Key="ImageBrush_Decrement" ImageSource="Images/pad-metronome-decrement-button.png" Stretch="Fill"/>
        <ImageBrush x:Key="ImageBrush_Increment" ImageSource="Images/pad-metronome-increment-button.png" Stretch="Fill"/>

    </ResourceDictionary>
</UserControl.Resources>
<UserControl.Triggers>
    <EventTrigger RoutedEvent="FrameworkElement.Loaded">

    </EventTrigger>
</UserControl.Triggers>

<Grid x:Name="LayoutRoot" Height="412">
    <Image x:Name="MetronomeWindowBackground" Height="140" Margin="237,1.5,231,0" Source="Images\pad-metronome-top-under-bg.png" Stretch="Fill" VerticalAlignment="Top"/>
    <Image x:Name="Arm" Margin="506,17,493,0" Source="Images\pad-metronome-arm.png" Stretch="Fill" Height="326" VerticalAlignment="Top" RenderTransformOrigin="0.5,0.5">
        <Image.RenderTransform>
            <TransformGroup>
                <RotateTransform/>

            </TransformGroup>
        </Image.RenderTransform>
    </Image>
    <Image x:Name="MetronomeFlash" Height="209" Margin="104,0,96,0" Source="Images\pad-metronome-flash-top-landscape.png" Stretch="Fill" VerticalAlignment="Top" d:IsHidden="True" />
    <Image x:Name="MetronomeBackground" Height="209" Source="Images\pad-metronome-top-bg-landscape.png" Stretch="Fill" VerticalAlignment="Top" Margin="3,0,-3,0"/>
    <Image x:Name="MetronomeStartButton" Margin="379.5,100.5,373.5,0" Source="Images\pad-metronome-start-button-base.png" Stretch="Fill" Height="110" VerticalAlignment="Top"/>
    <Image x:Name="MetronomeTapPadLeft" HorizontalAlignment="Left" Height="209" Margin="5,1.5,0,0" Source="Images\pad-metronome-tap-pad-left.png" Stretch="Fill" VerticalAlignment="Top" Width="136"/>
    <Image x:Name="MetronomeTapPadRight" HorizontalAlignment="Right" Source="Images\pad-metronome-tap-pad-right.png" Stretch="Fill" Width="136" Height="209" VerticalAlignment="Top"/>
    <Image x:Name="MetronomeWindowHighlight" Height="105" Margin="238.5,18,231.5,0" Source="Images\pad-metronome-window-overlay.png" Stretch="Fill" VerticalAlignment="Top"/>
    <Image x:Name="MetronomeBottomBackground" Margin="3,208,-3,362" Source="Images\pad-metronome-section-bottom-bg.png" Stretch="Fill"/>
    <my:MetronomeLargeNumericDisplay HorizontalAlignment="Left" Margin="459,120,0,0" x:Name="NumericDisplay" VerticalAlignment="Top" Value="999" Width="122.25" />
    <Image Height="78" Margin="448,110.5,436,0" Source="Images\pad-metronome-start-button-overlay.png" Stretch="Fill" VerticalAlignment="Top"
           x:Name="DisplayOverlay" MouseDown="DisplayOverlay_MouseDown" />
    <RepeatButton x:Name="ButtonDecrement" Content="" BorderThickness="7" HorizontalAlignment="Left" Margin="252,110.5,0,0" VerticalAlignment="Top" Width="149" Height="100" Background="{DynamicResource ImageBrush_Decrement}" Style="{DynamicResource RepeatButtonStyle_noflash}" BorderBrush="{DynamicResource ImageBrush_Decrement}" d:LayoutOverrides="HorizontalAlignment" Click="ButtonDecrement_Click"></RepeatButton>
    <RepeatButton Content="" BorderThickness="7" HorizontalAlignment="Left" Margin="631,110.5,0,0" VerticalAlignment="Top" Width="149" Height="100" Background="{DynamicResource ImageBrush_Increment}" Style="{DynamicResource RepeatButtonStyle_noflash}" BorderBrush="{DynamicResource ImageBrush_Decrement}" Name="ButtonIncrement" Click="ButtonIncrement_Click" />
</Grid>

what am I doing wrong?