stripes.xaml

<UserControl x:Class="WPFTestApp.Stripes"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             xmlns:local="clr-namespace:WPFTestApp"
             mc:Ignorable="d" Loaded="UserControl_Loaded" >
    
    <Border Name="border" BorderThickness="2" BorderBrush="Gray">
        <Rectangle Name="rect" Fill="{DynamicResource gradientBrush}">
            <Rectangle.Resources>
                <Color x:Key="backgroundcolor">#000000</Color>
                <Color x:Key="foregroundcolor">#FFFFFF</Color>
                <LinearGradientBrush x:Key="gradientBrush" StartPoint="0,0" EndPoint="1,1" />
                <Storyboard x:Key="storyBoard" />
            </Rectangle.Resources>
            
            <Rectangle.Triggers>
                <EventTrigger RoutedEvent="Loaded">
                    <BeginStoryboard Storyboard="{StaticResource storyBoard}" />
                </EventTrigger>
            </Rectangle.Triggers>
        </Rectangle>

    </Border>
</UserControl>

stripes.xaml.cs

using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Media;
using System.Windows.Media.Animation;

namespace WPFTestApp {
    /// <summary>
    /// Interaction logic for stripes.xaml
    /// </summary>
    public partial class Stripes : UserControl {
        public Stripes() {
            InitializeComponent();

            LinearGradientBrush brush = (LinearGradientBrush)rect.Resources["gradientBrush"];
            Storyboard storyBoard = (Storyboard)rect.Resources["storyBoard"];

            Binding backbind = new Binding("backgroundcolor");
            Binding forebind = new Binding("foregroundcolor");
            
            for (int x = 0; x < 33; x++) {
                string name = "GStop" + x.ToString();
                double offset = ((double)x * .05) - .4;

                GradientStop gstop = new GradientStop() { Offset = offset };
                brush.GradientStops.Add(gstop);
                gstop.SetValue(Control.NameProperty, name);

                if (x % 2 == 0) {
                    BindingOperations.SetBinding(gstop, GradientStop.ColorProperty, backbind);
                } else {
                    BindingOperations.SetBinding(gstop, GradientStop.ColorProperty, forebind);
                }

                

                DoubleAnimation ani = new DoubleAnimation() {
                    By = .2,
                    Duration = new TimeSpan(0, 0, 1),
                    RepeatBehavior = RepeatBehavior.Forever
                };

                BindingOperations.SetBinding(ani, Storyboard.TargetPropertyProperty, new Binding("Offset"));
                BindingOperations.SetBinding(ani, Storyboard.TargetNameProperty, new Binding(name));

                storyBoard.Children.Add(ani);

            }

        }


        public Color BackGroundColor
        {
            get { return (Color)rect.Resources["backgroundcolor"]; }
            set { rect.Resources["backgroundcolor"] = value; }
        }

        public Color ForeGroundColor
        {
            get { return (Color)rect.Resources["foregroundcolor"]; }
            set { rect.Resources["foregroundcolor"] = value; }
        }

        private void UserControl_Loaded(object sender, RoutedEventArgs e) {

            double size = (Width > Height ? Width : Height);

            rect.Height = size;
            rect.Width = size;
        }
    }
}