Code source

<UserControl
    x:Name="this"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
    xmlns:System="clr-namespace:System;assembly=mscorlib"
    xmlns:i="clr-namespace:System.Windows.Interactivity;assembly=System.Windows.Interactivity"
    xmlns:im="clr-namespace:Microsoft.Expression.Interactivity.Media;assembly=Microsoft.Expression.Interactions"
    mc:Ignorable="d" d:DesignHeight="300" d:DesignWidth="300">

    <UserControl.Resources>
        <!--Below this value: trigger: StopAnimation-->
        <System:Double x:Key="AnimationStop">100</System:Double>
        <!--Above or equal this value: trigger: StartAnimation-->
        <System:Double x:Key="AnimationStart">150</System:Double>
        <!--Invert the trigger behavior-->
        <System:Boolean x:Key="AnimationTriggerInvert">False</System:Boolean>


        <Style TargetType="{x:Type Image}">
            <Setter Property="RenderTransform">
                <Setter.Value>
                    <RotateTransform Angle="0" CenterX="20" CenterY="18" />
                </Setter.Value>
            </Setter>
        </Style>

        <Storyboard x:Key="sb" >
            <DoubleAnimation 
                Storyboard.TargetName="myImg"
                Storyboard.TargetProperty="RenderTransform.Angle"   
                From="0"
                To="360"                
                Duration="0:0:5"
                SpeedRatio="1"
                RepeatBehavior="Forever">
            </DoubleAnimation>
        </Storyboard>

    </UserControl.Resources>

    <Grid>



        <Image  
            x:Name="myImg"            
            Source="Content/images/running_fan_black.png"
            Opacity="1.0"
            Height="40" 
            Width="40" 
            Margin="0,0,0,0"             
            Stretch="Uniform" 
            StretchDirection="Both">

            <i:Interaction.Triggers>
                <i:EventTrigger SourceObject="{Binding ElementName=this, Path=DataContext}" EventName="StartAnimation">
                    <im:ControlStoryboardAction Storyboard="{StaticResource sb}" ControlStoryboardOption="Play"/>
                </i:EventTrigger>
                <i:EventTrigger SourceObject="{Binding ElementName=this, Path=DataContext}" EventName="StopAnimation">
                    <im:ControlStoryboardAction Storyboard="{StaticResource sb}" ControlStoryboardOption="Stop"/>
                </i:EventTrigger>
            </i:Interaction.Triggers>

        </Image>
    </Grid>
</UserControl>