LinearGradientBrush 到 Transparency 显示白色背景

Question

我有 background 颜色 #424242 和 ListBox 以及一些内容..

我想在控件顶部有一个从 #424242 到 Transparent 的 LinearGradientBrush。问题是，我得到了白色背景颜色：

如果我用 #00000000 替换 Transparent 我有一个 darker/black 颜色：

XAML代码

<Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="136*"/>
            <RowDefinition Height="203*"/>
        </Grid.RowDefinitions>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="*"/>
            <ColumnDefinition Width="*"/>
            <ColumnDefinition Width="*"/>
        </Grid.ColumnDefinitions>
        <StackPanel Orientation="Vertical" Grid.Column="0" Grid.Row="0" HorizontalAlignment="Center">
            <TextBlock Text="Transparent to #424242"></TextBlock>
            <TextBlock Text="Transparent to #424242"></TextBlock>
            <TextBlock Text="Transparent to #424242"></TextBlock>
            <TextBlock Text="Transparent to #424242"></TextBlock>
            <TextBlock Text="Transparent to #424242"></TextBlock>
            <TextBlock Text="Transparent to #424242"></TextBlock>
            <TextBlock Text="Transparent to #424242"></TextBlock>
            <TextBlock Text="Transparent to #424242"></TextBlock>
            <TextBlock Text="Transparent to #424242"></TextBlock>
            <TextBlock Text="Transparent to #424242"></TextBlock>
            <TextBlock Text="Transparent to #424242"></TextBlock>
            <TextBlock Text="Transparent to #424242"></TextBlock>
            <TextBlock Text="Transparent to #424242"></TextBlock>
            <TextBlock Text="Transparent to #424242"></TextBlock>
            <TextBlock Text="Transparent to #424242"></TextBlock>
        </StackPanel>
        <Rectangle Grid.Column="0" Grid.Row="0">
            <Rectangle.Fill>
                <LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
                    <GradientStop Color="Transparent" Offset="0"/>
                    <GradientStop Color="#424242" Offset="1"/>
                </LinearGradientBrush>
            </Rectangle.Fill>
        </Rectangle>

        <StackPanel Orientation="Vertical" Grid.Column="1" Grid.Row="0" HorizontalAlignment="Center">
            <TextBlock Text="#00000000 to #424242"></TextBlock>
            <TextBlock Text="#00000000 to #424242"></TextBlock>
            <TextBlock Text="#00000000 to #424242"></TextBlock>
            <TextBlock Text="#00000000 to #424242"></TextBlock>
            <TextBlock Text="#00000000 to #424242"></TextBlock>
            <TextBlock Text="#00000000 to #424242"></TextBlock>
            <TextBlock Text="#00000000 to #424242"></TextBlock>
            <TextBlock Text="#00000000 to #424242"></TextBlock>
            <TextBlock Text="#00000000 to #424242"></TextBlock>
            <TextBlock Text="#00000000 to #424242"></TextBlock>
            <TextBlock Text="#00000000 to #424242"></TextBlock>
            <TextBlock Text="#00000000 to #424242"></TextBlock>
            <TextBlock Text="#00000000 to #424242"></TextBlock>
            <TextBlock Text="#00000000 to #424242"></TextBlock>
            <TextBlock Text="#00000000 to #424242"></TextBlock>
        </StackPanel>
        <Rectangle Grid.Column="1" Grid.Row="0">
            <Rectangle.Fill>
                <LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
                    <GradientStop Color="#00000000" Offset="0"/>
                    <GradientStop Color="#424242" Offset="1"/>
                </LinearGradientBrush>
            </Rectangle.Fill>
        </Rectangle>

        <StackPanel Orientation="Vertical" Grid.Column="2" Grid.Row="0" HorizontalAlignment="Center">
            <TextBlock Text="Hello World"></TextBlock>
            <TextBlock Text="Hello World"></TextBlock>
            <TextBlock Text="Hello World"></TextBlock>
            <TextBlock Text="Hello World"></TextBlock>
            <TextBlock Text="Hello World"></TextBlock>
            <TextBlock Text="Hello World"></TextBlock>
            <TextBlock Text="Hello World"></TextBlock>
            <TextBlock Text="Hello World"></TextBlock>
            <TextBlock Text="Hello World"></TextBlock>
            <TextBlock Text="Hello World"></TextBlock>
            <TextBlock Text="Hello World"></TextBlock>
            <TextBlock Text="Hello World"></TextBlock>
            <TextBlock Text="Hello World"></TextBlock>
            <TextBlock Text="Hello World"></TextBlock>
            <TextBlock Text="Hello World"></TextBlock>
        </StackPanel>
        <Rectangle Grid.Column="2" Grid.Row="0" Opacity="0">
            <Rectangle.Fill>
                <LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
                    <GradientStop Color="#424242" Offset="0"/>
                    <GradientStop Color="#424242" Offset="1"/>
                </LinearGradientBrush>
            </Rectangle.Fill>
        </Rectangle>
    </Grid>
</Grid>

Answer 1

我有答案：只需使用与 Alpha 0% 相同的颜色

<Rectangle.Fill>
    <LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
        <GradientStop Color="#FF424242" Offset="1"/>
        <GradientStop Color="#00424242"/>
    </LinearGradientBrush>
</Rectangle.Fill>

LinearGradientBrush 到 Transparency 显示白色背景

LinearGradientBrush to Transparency shows white background

c#

wpf

expression-blend

XAML代码