为什么我的硬编码气球中的进度条前景颜色没有改变

Question

我正在使用WPF NotifyIcon并使用此Balloon：

<UserControl
    x:Class="PacketPlayer.ApplicationBalloon"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:tb="http://www.hardcodet.net/taskbar"
    Height="130"
    Width="283"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:my="clr-namespace:PacketPlayer.classes"
    mc:Ignorable="d"
    x:Name="me">
    <UserControl.Resources>
        <Storyboard
            x:Key="FadeInAndOut">
            <DoubleAnimationUsingKeyFrames
                BeginTime="00:00:00"
                Storyboard.TargetName="grid"
                Storyboard.TargetProperty="(UIElement.Opacity)">
                <SplineDoubleKeyFrame
                    KeyTime="00:00:00"
                    Value="0" />
                <SplineDoubleKeyFrame
                    KeyTime="00:00:01"
                    Value="0.895" />
                <SplineDoubleKeyFrame
                    KeyTime="00:00:10"
                    Value="0.895" />
                <SplineDoubleKeyFrame
                    KeyTime="00:00:11.6000000"
                    Value="0" />
            </DoubleAnimationUsingKeyFrames>
        </Storyboard>
    </UserControl.Resources>
    <UserControl.Triggers>
        <EventTrigger
            RoutedEvent="tb:TaskbarIcon.BalloonShowing">
            <BeginStoryboard
                Storyboard="{StaticResource FadeInAndOut}"
                x:Name="FadeInAndOut_BeginStoryboard" />
        </EventTrigger>
    </UserControl.Triggers>
    <Grid
        x:Name="grid">
        <Border
            x:Name="border"
            CornerRadius="10,10,10,10"
            Margin="0,0,5,5">
            <Border.Background>
                <LinearGradientBrush
                    EndPoint="0.5,1"
                    StartPoint="0.5,0">
                    <GradientStop
                        Color="#FFEEEEEE"
                        Offset="1" />
                    <GradientStop
                        Color="#FF474E5B"
                        Offset="0" />
                </LinearGradientBrush>
            </Border.Background>
            <Border.Effect>
                <DropShadowEffect />
            </Border.Effect>
        </Border>
        <StackPanel Orientation="Vertical" Margin="10,10,0,0">
            <TextBlock
                VerticalAlignment="Top"
                FontSize="18"
                FontWeight="Bold"            
                TextWrapping="Wrap"
                Text="Packet Player still running..."
                Foreground="White"
                Margin="0,0,0,0"/>
            <StackPanel Orientation="Horizontal" Margin="0,0,0,0">
                <ProgressBar
                    Name="progressBar"
                    Width="180"
                    BorderBrush="White"
                    Value="0"
                    Height="20"
                    Foreground="Yellow"
                    Background="Transparent"
                    HorizontalAlignment="Left"
                    Margin="0,12,0,0"/>
                <TextBlock
                    Name="tbProgressBarPercent"
                    Text="0%"
                    Foreground="White"
                    FontSize="16"
                    Margin="7,11,0,0"/>
            </StackPanel>
            <Label
                ContentStringFormat="{}{0:#,0} Packets sent"
                HorizontalAlignment="Left"
                Foreground="White"
                Margin="-5,8,0,0"/>
        </StackPanel>
    </Grid>
</UserControl>

在Balloon内部我放简单Progress Bar并通过代码behond更改它的值。

<ProgressBar
    Name="progressBar"
    Width="180"
    Height="25"
    BorderBrush="Black"
    Value="24"
    Background="Transpare
    Foreground="Yellow"/>

progressBar.Value = "33;

我唯一的问题是我可以更改所有Progress Bar属性，Forecolor无效。