Xml 设置按钮样式时出现问题

我正在将以下样式设置为按钮：

<Style x:Key="CustomButtonStyle1" TargetType="Button">
            <Setter Property="Background" Value="Transparent"/>
            <Setter Property="BorderBrush" Value="{StaticResource PhoneForegroundBrush}"/>
            <Setter Property="Foreground" Value="{StaticResource PhoneForegroundBrush}"/>
            <Setter Property="BorderThickness" Value="{StaticResource PhoneBorderThickness}"/>
            <Setter Property="FontFamily" Value="{StaticResource PhoneFontFamilySemiBold}"/>
            <Setter Property="FontSize" Value="{StaticResource PhoneFontSizeMediumLarge}"/>
            <Setter Property="Padding" Value="10,3,10,5"/>
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="Button">
                        <Grid Background="Transparent">
                            <VisualStateManager.VisualStateGroups>
                                <VisualStateGroup x:Name="CommonStates">
                                    <VisualState x:Name="Normal"/>
                                    <VisualState x:Name="MouseOver"/>
                                    <VisualState x:Name="Pressed" />
                                    <VisualState x:Name="Disabled"/>
                                    <Storyboard>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Foreground" Storyboard.TargetName="ContentContainer">
                                            <DiscreteObjectKeyFrame KeyTime="0" Value="White"/>
                                        </ObjectAnimationUsingKeyFrames>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="BorderBrush" Storyboard.TargetName="ButtonBackground">
                                            <DiscreteObjectKeyFrame KeyTime="0" Value="{StaticResource PhoneDisabledBrush}"/>
                                        </ObjectAnimationUsingKeyFrames>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Background" Storyboard.TargetName="ButtonBackground">
                                                <DiscreteObjectKeyFrame KeyTime="0">
                                                    <DiscreteObjectKeyFrame.Value>
                                                        <ImageBrush ImageSource="Images/aaa2.png"/>
                                                    </DiscreteObjectKeyFrame.Value>
                                                </DiscreteObjectKeyFrame>
                                            </ObjectAnimationUsingKeyFrames>
                                        </Storyboard>
                                </VisualStateGroup>
                            </VisualStateManager.VisualStateGroups>
                            <Border x:Name="ButtonBackground" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" CornerRadius="0" Margin="{StaticResource PhoneTouchTargetOverhang}">
                                <ContentControl x:Name="ContentContainer" ContentTemplate="{TemplateBinding ContentTemplate}" Content="{TemplateBinding Content}" Foreground="{TemplateBinding Foreground}" HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}" Padding="{TemplateBinding Padding}" VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}"/>
                            </Border>
                        </Grid>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>  

但是，我遇到以下错误，我不知道如何解决：

错误1无法将类型为“System.Windows.Media.Animation.Storyboard”的实例添加到类型为“MS.Internal”的集合中。！VisualStateCollection’。[第23行位置：17]

按钮定义如下：

<StackPanel Orientation="Horizontal" HorizontalAlignment="Center" Margin="0,30,0,0">
                <Button Name="aaa" Width="200" Content="aaa" Margin="0,0,-10,0" Click="aaa_Click" BorderThickness="0" BorderBrush="{x:Null}" Height="91" Foreground="Black" Style="{StaticResource CustomButtonStyle1}">
                    <Button.Background>
                        <ImageBrush ImageSource="../Images/aaa.png"/>
                    </Button.Background>
                </Button>

---

故事板应位于VisualState中

<VisualState x:Name="Pressed"> 
<Storyboard>...</Storyboard>
</VisualState>