<Window x:Class="DynamicallyBindingToALogicalResource.MainWindow"

        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

        Title="MainWindow" Height="350" Width="525">

    <Window.Resources>

        <LinearGradientBrush x:Key="brush1">

            <GradientStop Offset="0.3" Color="Yellow"/>

            <GradientStop Offset="0.7" Color="Brown"/>

        </LinearGradientBrush>

    </Window.Resources>

    <StackPanel>

        <Rectangle Height="100" Stroke="Pink" StrokeThickness="20" Fill="{StaticResource brush1}"/>

        <Rectangle Height="100" Stroke="Violet" StrokeThickness="20" Fill="{DynamicResource brush1}" />

        <Button x:Name="button1" Content="Replace Brush" Height="100" Click="OnReplaceBrush"/>

    </StackPanel>

</Window>

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.Media;

using System.Windows.Media.Imaging;

using System.Windows.Navigation;

using System.Windows.Shapes;

namespace DynamicallyBindingToALogicalResource

{

    /// <summary>

    /// Interaction logic for MainWindow.xaml

    /// </summary>

    public partial class MainWindow : Window

    {

        public MainWindow()

        {

            InitializeComponent();

        }

        private void OnReplaceBrush(object sender, RoutedEventArgs e)

        {

            var brush = new LinearGradientBrush();

            brush.GradientStops.Add(new GradientStop(Colors.Pink, 0.2));

            brush.GradientStops.Add(new GradientStop(Colors.Blue, 0.5));

            brush.GradientStops.Add(new GradientStop(Colors.Violet, 0.8));

            this.Resources["brush1"] = brush;

        }

    }

}