不透明蒙版方向从上到下？

Question

我想从上到下淡化 wpf 文本框的文本。不是从左到右。有没有办法在 xaml 中做到这一点？以下是我目前所拥有的

<TextBox x:Name="txtDesc" Text="{x:Static model:CarManager.Desc}" VerticalAlignment="Top" HorizontalAlignment="Left" TextWrapping="Wrap" VerticalScrollBarVisibility="Auto"  Width="466"  FontWeight="Bold" Height="263" Margin="304,195,0,0" BorderBrush="{x:Null}" BorderThickness="0" Background="{x:Null}">
        <TextBox.Foreground>
            <LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
                <GradientStop Color="#FF8F8F8F" Offset="0"/>
                <GradientStop Color="White"/>
            </LinearGradientBrush>
        </TextBox.Foreground>
        <TextBox.OpacityMask>
            <LinearGradientBrush StartPoint="0,0" EndPoint="1,0">
                <GradientStop Offset="0" Color="WhiteSmoke"></GradientStop>
                <GradientStop Offset="1" Color="Transparent"></GradientStop>
            </LinearGradientBrush>
        </TextBox.OpacityMask>
    </TextBox>

这会从左到右淡化文本。我想从上到下淡化它。

感谢您的帮助

Answer 1

使用这个

    <TextBox x:Name="txtDesc" Text="{x:Static model:CarManager.Desc}" VerticalAlignment="Top" HorizontalAlignment="Left" TextWrapping="Wrap" VerticalScrollBarVisibility="Auto"  Width="466"  FontWeight="Bold" Height="263" Margin="304,195,0,0" BorderBrush="{x:Null}" BorderThickness="0" Background="{x:Null}">
        <TextBox.Foreground>
            <LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
                <GradientStop Color="#FF8F8F8F" Offset="0"/>
                <GradientStop Color="White"/>
            </LinearGradientBrush>
        </TextBox.Foreground>
        <TextBox.OpacityMask>
            <LinearGradientBrush StartPoint="0.5,0" EndPoint="0.5,1">
                <GradientStop Offset="0" Color="WhiteSmoke"></GradientStop>
                <GradientStop Offset="1" Color="Transparent"></GradientStop>
            </LinearGradientBrush>
        </TextBox.OpacityMask>
    </TextBox>