<Button xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Height="100" Width="100" Content="OK">
    <Button.LayoutTransform>
        <RotateTransform Angle="0" x:Name="rotateTransform"/>
    </Button.LayoutTransform>
    <Button.Triggers>
        <EventTrigger RoutedEvent="Button.MouseEnter">
            <BeginStoryboard HandoffBehavior="Compose">
                <Storyboard>
                    <DoubleAnimation 
                     Storyboard.TargetName="rotateTransform"
                     Duration="0:0:1" Storyboard.TargetProperty="Angle" To="720"/>
                </Storyboard>
            </BeginStoryboard>
        </EventTrigger>
        <EventTrigger RoutedEvent="Button.MouseLeave">
            <BeginStoryboard HandoffBehavior="Compose">
                <Storyboard>
                    <DoubleAnimation 
                     Storyboard.TargetName="rotateTransform"
                     Duration="0:0:1" Storyboard.TargetProperty="Angle"/>
                </Storyboard>
            </BeginStoryboard>
        </EventTrigger>
    </Button.Triggers>
</Button>
