wpf-为TextBox设置部分背景

最初方案

最开始我想的是放一个矩形，调整margin和width，盖住就好了。写完我感觉我傻逼了，因为这样的话，TextBox的内容是无法复制的。。。不过倒是get了如何用LinearGradientBrush填充单一色块。

<Grid Grid.Row="1" Height="200">
    <Grid.RowDefinitions>
        <RowDefinition Height="auto"/>
        <RowDefinition Height="auto"/>
        <RowDefinition Height="auto"/>
        <RowDefinition Height="auto"/>
        <RowDefinition Height="auto"/>
    </Grid.RowDefinitions>
    <TextBox Grid.Row="0" Text="TTAGCCT" Margin="0" FontFamily="Courier New" FontSize="18.01" VerticalAlignment="Bottom"/>
    <TextBlock Grid.Row="1" Text="|||||||" Margin="0" FontFamily="Courier New" FontSize="18.01" VerticalAlignment="Top"/>
    <TextBox Grid.Row="2" Text="AATCGGA" Margin="0" FontFamily="Courier New" FontSize="18.01" VerticalAlignment="Top"/>
    <Rectangle Grid.Row="0" Grid.RowSpan="3" Visibility="Visible" x:Name="myRec" Opacity="0.35" Margin="24,0,0,0" >
        <Rectangle.Fill>
            <LinearGradientBrush StartPoint="0,0" EndPoint="1,0" >
                <GradientStop Color="LightBlue" Offset="0"/>
                <GradientStop Color="LightBlue" Offset="0.18"/>
                <GradientStop Color="White" Offset="0.18"/>
                <GradientStop Color="White" Offset="1.0"/>
                <LinearGradientBrush.Transform >
                    <TranslateTransform X="0.1"/>
                </LinearGradientBrush.Transform>
            </LinearGradientBrush>
        </Rectangle.Fill>
    </Rectangle>
    <Button Grid.Row="3" Content="click" Width="40"  Click="Button_Click"/>
</Grid>

最终方案

在后台改写TextBox的background，通过调整GradientStop控制位置和长度。start和end就根据控件的长度/字符的长度之类的自己调吧。。。

<Grid Grid.Row="1" Height="200">
    <Grid.RowDefinitions>
        <RowDefinition Height="auto"/>
        <RowDefinition Height="auto"/>
        <RowDefinition Height="auto"/>
        <RowDefinition Height="auto"/>
        <RowDefinition Height="auto"/>
    </Grid.RowDefinitions>
    <Border Grid.Row="0" Grid.RowSpan="5" Background="Bisque" />
    <TextBox x:Name="mybox" Grid.Row="0" Text="TTAGCCT" Margin="0" FontFamily="Courier New" FontSize="18.01" VerticalAlignment="Bottom"/>
    <TextBlock Grid.Row="1" Text="|||||||" Margin="0" FontFamily="Courier New" FontSize="18.01" VerticalAlignment="Top"/>
    <TextBox Grid.Row="2" Text="AATCGGA" Margin="0" FontFamily="Courier New" FontSize="18.01" VerticalAlignment="Top"/>
    <Button Grid.Row="3" Content="click" Width="40"  Click="Button_Click"/>
</Grid>

后台

private LinearGradientBrush GetBlockBackground(double start, double end) {
    
    
    LinearGradientBrush lgb = new LinearGradientBrush();
    // 只需要水平渐变
    lgb.StartPoint = new Point(0, 0);
    lgb.EndPoint = new Point(1, 0);
    // 左侧透明块
    GradientStop gs1 = new GradientStop();
    gs1.Color = Colors.Transparent;
    gs1.Offset = 0;
    lgb.GradientStops.Add(gs1);
    // 蓝色开始位置
    GradientStop gs2 = new GradientStop();
    gs2.Color = Colors.Transparent;
    gs2.Offset = start;
    lgb.GradientStops.Add(gs2);
    // 同一位置设置两种颜色的GradientStop
    GradientStop gs22 = new GradientStop();
    gs22.Color = Colors.LightBlue;
    gs22.Offset = start;
    lgb.GradientStops.Add(gs22);
    // 蓝色结束位置
    GradientStop gs3 = new GradientStop();
    gs3.Color = Colors.LightBlue;
    gs3.Offset = end;
    lgb.GradientStops.Add(gs3);
    // 同一位置设置两种颜色的GradientStop
    GradientStop gs33 = new GradientStop();
    gs33.Color = Colors.Transparent;
    gs33.Offset = end;
    lgb.GradientStops.Add(gs33);
    // 右侧结束
    GradientStop gs4 = new GradientStop();
    gs4.Color = Colors.Transparent;
    gs4.Offset = 1.0;
    lgb.GradientStops.Add(gs4);
    return lgb;
}

private void Button_Click(object sender, RoutedEventArgs e)
{
    
    
    this.mybox.Background = GetBlockBackground(0.026, 0.044);
}