CryptedTextAnimation.cs

using System;
using System.Text;
using System.Windows;
using System.Windows.Media.Animation;

namespace leMaik.Animations {
    class CryptedTextAnimation : AnimationTimeline {
        static CryptedTextAnimation() {
            LengthProperty = DependencyProperty.Register("Length", typeof(int), typeof(CryptedTextAnimation));
        }
        public static readonly DependencyProperty LengthProperty;
        public int Length {
            get {
                return (int)GetValue(CryptedTextAnimation.LengthProperty);
            }
            set {
                SetValue(CryptedTextAnimation.LengthProperty, value);
            }
        }

        private const String CHARACTERS = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789+#-.?!";
        private Random randomizer = new Random(Environment.TickCount);
        private String previousString = String.Empty;

        public override Type TargetPropertyType {
            get { return typeof(String); }
        }

        protected override System.Windows.Freezable CreateInstanceCore() {
            return new CryptedTextAnimation();
        }

        public override object GetCurrentValue(object defaultOriginValue, object defaultDestinationValue, AnimationClock animationClock) {
            if (animationClock.CurrentTime.Value.TotalSeconds % 0.5 < 0.5) {
                StringBuilder str = new StringBuilder(Length);
                for (int i = 0; i < Length; i++) {
                    str.Append(CHARACTERS[randomizer.Next(CHARACTERS.Length)]);
                }
                previousString = str.ToString();
            }

            return previousString;
        }
    }
}