Remove an attribute from xaml using c# - WPF - wpf

Question

This question is related to removing an attribute in xaml.
In the below code, I have a Span. During an event, I add a back ground to this Span. During another event, I need to remove it. Please let me know, if there is a way to remove the background attribute I set to Span.
My Xaml looks like this.
<Window x:Class="WpfApplication4.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:local="clr-namespace:WpfApplication4"
mc:Ignorable="d"
Title="MainWindow" Height="350" Width="525">
<Grid>
<Grid.RowDefinitions>
<RowDefinition></RowDefinition>
<RowDefinition></RowDefinition>
<RowDefinition Height="40"></RowDefinition>
</Grid.RowDefinitions>
<RichTextBox x:Name="rtb">
<FlowDocument>
<Paragraph>
<Span x:Name="def" Tag="default">
<Run x:Name="deg">Some Text</Run>
</Span>
</Paragraph>
</FlowDocument>
</RichTextBox>
<TextBox x:Name="tx" Grid.Row="1" TextWrapping="Wrap"/>
<Grid Grid.Row="2">
<Grid.ColumnDefinitions>
<ColumnDefinition/>
<ColumnDefinition/>
<ColumnDefinition/>
</Grid.ColumnDefinitions>
<Button Content="s" Click="Button_Click"/>
<Button Content="bg-Add" Grid.Column="1" Click="Button_Click"/>
<Button Content="bg-Remove" Grid.Column="2" Click="Button_Click"/>
</Grid>
</Grid>
</Window>
My code looks like this.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Markup;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows. Shapes;
namespace WpfApplication4
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
}
private void Button_Click(object sender, RoutedEventArgs e)
{
if ((sender as Button).Content.ToString() == "s")
{
tx.Text = XamlWriter.Save(def);
}
else if ((sender as Button).Content.ToString() == "bg-Add")
{
def.Background = new SolidColorBrush(Colors.Blue);
}
else if ((sender as Button).Content.ToString() == "bg-Remove")
{
//Need to remove the set back color so that I get the default back
}
}
}
}

Answer 1

I am able to find an answer myself.
def.ClearValue(Span.BackgroundProperty);
is going to remove that attribute for me.

Answer 2

You can override ShouldSerializeProperty
public class CustomizedSpan : Span
{
public bool IsRemoveBackGround;
protected override bool ShouldSerializeProperty(DependencyProperty dp)
{
if (dp == Span.BackgroundProperty && IsRemoveBackGround)
{
return false;
}
else
{
return base.ShouldSerializeProperty(dp);
}
}
}